Workiva/over

OverReact

A library for building statically-typed React UI components using Dart.

This library also exposes OverReact Redux, which has its own documentation.

Migration Guides
Using OverReact
- Running tests in your project
  - OverReact Component Unit Test Examples
Anatomy of an OverReact component
Fluent-style component consumption
DOM components and props
Component Formatting
Building custom components
- Component Boilerplates
- Component Best Practices
Contributing

Migration Guides

Null safety

over_react 5.0.0 introduces support for null safety.

Now, you can declare non-nullable required props, using the late keyword. See the docs null safety and required props for more information.

To migrate components to null safety, see our null safety migration guide.

More Migration Guides

New component boilerplate: How to update to the mixin-based (mixin MyProps on UiProps {}) over_react component declaration syntax.
UiComponent2: How to move off the deprecated UiComponent base class and onto UiComponent2.
BuiltRedux to Redux: How to transition to OverReact Redux from BuiltRedux.
Flux to Redux: A guide to how to transition from w_flux to OverReact Redux. This guide also introduces a new architecture, Influx, that can be used for incremental refactors.
Dart2 Migration: Documentation on the Dart 2 builder updates and how to transition componentry to Dart 2.

Using OverReact

Prerequisites

Familiarize yourself with React JS

Since OverReact is built atop React JS, we strongly encourage you to gain familiarity with it by reading some React JS tutorials first.

Familiarize yourself with Dart Web applications

If you have never built a Web application in Dart, we strongly encourage you to gain familiarity with the core terminology, tools and boilerplate necessary to serve an application locally using Dart. Dart has fantastic documentation and tutorials to get you started.

Add the over_react package as a dependency in your pubspec.yaml.
```
dependencies:
  over_react: ^4.0.0
```
Enable the OverReact Analyzer Plugin (beta), which has many lints and assists to make authoring OverReact components easier!

Include the native JavaScript react and react_dom libraries in your app’s index.html file, and add an HTML element with a unique identifier where you’ll mount your OverReact UI component(s).

<html>
  <head>
    <!-- ... -->
  </head>
  <body>
    <div id="react_mount_point">
      // OverReact component render() output will show up here.
    </div>

    <script src="packages/react/js/react.dev.js"></script>

    <!-- NOTE: "index" should correspond to the
         name of the `.dart` file that contains your `main()` entrypoint. -->
    <script type="application/javascript" defer src="index.dart.js"></script>
  </body>
</html>

Note: When serving your application in production, use packages/react/js/react.min.js file instead of the un-minified packages/react/js/react.dev.js file shown in the example above.

Import the over_react and react_dom libraries into index.dart. Then build some components and mount / render a React tree within the HTML element you created in the previous step by calling react_dom.render() within the main() entrypoint of your Dart application.

Be sure to namespace the react_dom.dart import as react_dom to avoid collisions with UiComponent.render when creating custom components.

import 'dart:html';
import 'package:over_react/react_dom.dart' as react_dom;
import 'package:over_react/over_react.dart';

// Example of where the `Foo` component might be exported from
import 'package:your_package_name/foo.dart';

main() {
  // Mount / render your component/application.
  react_dom.render(
    Foo()(),
    querySelector('#react_mount_point'),
  );
}

Run webdev serve in the root of your Dart project.

Note: If you're not using the latest component boilerplate, you'll have to restart your analysis server in your IDE for the built types to resolve properly after the build completes. Unfortunately, this is a known limitation in the analysis server at this time.

Migrate your components to the latest component boilerplate to never worry about this again!

Running unit tests in your project

When running unit tests on code that uses the over_react builder (or any code that imports over_react), you must run your tests using the build_runner package.

Warning: Do not run tests via pub run build_runner test in a package while another instance of build_runner (e.g. pub run build_runner serve) is running in that same package. This workflow is unsupported by build_runner

Run tests using the build_runner package, and specify the platform to be a browser platform. Example:
```
$ pub run build_runner test -- -p chrome test/your_test_file.dart
```

OverReact Component Unit Test Examples

Below are links to a UI component from our example "Todo App", and its analogous tests that we've written for components we use in . We utilize the utilities found in our over_react_test library.

TodoListItem

Anatomy of an OverReact component

If you are not familiar with React JS

Since OverReact is built atop React JS, we strongly encourage you to gain familiarity with it by reading this React JS tutorial first.

The over_react library functions as an additional "layer" atop the Dart react package which handles the underlying JS interop that wraps around React JS.

The library strives to maintain a 1:1 relationship with the React JS component class and API. To do that, an OverReact component is comprised of four core pieces that are each wired up via our builder.

UiFactory
UiProps
component, either a:
1. function component uiFunction
2. class component UiComponent2 (and optionally a UiState)

UiFactory

UiFactory is a function that returns a new instance of a component's UiProps class.

// Class component
UiFactory<FooProps> Foo = castUiFactory(_$Foo);

// Function component
UiFactory<FooProps> Foo = uiFunction((props) { /*...*/ }, _$FooConfig);

This factory is the entry-point to consuming any OverReact component.
The UiProps instance it returns can be used as a component builder, or as a typed view into an existing props map.
castUiFactory is necessary to prevent implicit cast analysis warnings before code generation has been run.

UiProps

UiProps is a Map class that adds statically-typed getters and setters for each React component prop. It can also be invoked as a function, serving as a builder for its analogous component.

mixin FooProps on UiProps {
  // ... the props for your component go here
  String? bar;
  bool? baz;
  List<int>? bizzles;
}

- Note: The builder generates a class with getters and setters overriding the fields you declare in your mixin, but you don't need to worry about that generated class. To use props from another mixin, simply mix it in! See "With other mixins" below for more information.

With other mixins

To compose props mixin classes, create a class alias that uses UiProps as the base and mix in multiple props mixins. The generated props implementation will then use it as the base class and implement the generated version of those props mixins.

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooPropsMixin on UiProps {
  String? bar;
  bool? baz;
  List<int>? bizzles;
}

class FooProps = UiProps with FooPropsMixin, BarPropsMixin;

class FooComponent extends UiComponent2<FooProps> {
  // ...
}

Composition

The use-case for composing multiple props mixins into a single component props class is typically a component that renders another component, and therefore needs to expose the prop interface of that child component which will get forwarded via addUnconsumedProps.

Check out an example of props mixin component composition here

UiProps as a Map

Warning

Directly reading late required props on arbitrary maps is unsafe.

See the docs on Unsafe Required Prop Reads for more information and for instructions on how to read these props safely.

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooProps on UiProps {
  String? color;
}

class FooComponent extends UiComponent2<FooProps> {
  // ...
}

void bar() {
  FooProps props = Foo();

  props.color = '#66cc00';

  print(props.color); // #66cc00
  print(props);       // {FooProps.color: #66cc00}
}

/// You can also use the factory to create a UiProps instance
/// backed by an existing Map.
void baz() {
  Map existingMap = {'FooProps.color': '#0094ff'};

  FooProps props = Foo(existingMap);

  print(props.color); // #0094ff
}

UiProps as a builder

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooProps on UiProps {
  String? color;
}

class FooComponent extends UiComponent2<FooProps> {
  ReactElement bar() {
    // Create a UiProps instance to serve as a builder
    FooProps builder = Foo();

    // Set some prop values
    builder
      ..id = 'the_best_foo'
      ..color = '#ee2724';

    // Invoke as a function with the desired children
    // to return a new instance of the component.
    return builder('child1', 'child2');
  }

  /// Even better... do it inline! (a.k.a fluent)
  ReactElement baz() {
    return (Foo()
      ..id = 'the_best_foo'
      ..color = 'red'
    )(
      'child1',
      'child2'
    );
  }
}

See fluent-style component consumption for more examples on builder usage.

UiState

UiState is a Map class (just like UiProps) that adds statically-typed getters and setters for each React component state property in a class component.

mixin FooState on UiState {
  // ...
}

UiState is optional, and won’t be used for every component. Check out the UiStatefulComponent boilerplate for more information.

Note: The builder will make the concrete getters and setters available from the mixin fields you author in a generated class. To mix state classes together, the mixin class should be used rather than the generated props class. See "With other mixins" above for more information.

UiComponent2 (class-based components)

For guidance on updating to UiComponent2 from UiComponent, check out the UiComponent2 Migration Guide.

UiComponent2 is a subclass of react.Component2, containing lifecycle methods and rendering logic for components.

class FooComponent extends UiComponent2<FooProps> {
  // ...
}

This class provides statically-typed props via UiProps, as well as utilities for prop forwarding and CSS class merging.
The UiStatefulComponent2 flavor augments UiComponent2 behavior with statically-typed state via UiState.

uiFunction (function components)

uiFunction lets you declare a function component.

In JavaScript, function components are just plain functions, but in over_react this wrapper is needed to perform JS interop and wire up the typed props class.

mixin FooProps on UiProps {
  bool? isDisabled;
  List? items;
}

UiFactory<FooProps> Foo = uiFunction((props) {
  // Set default props using null-aware operators.
  final isDisabled = props.isDisabled ?? false;
  final items = props.items ?? [];

  // Return the rendered component contents here.
  return Fragment()(
    Dom.div()(items),
    (Dom.button()..disabled = isDisabled)('Click me!'),
  );
}, _$FooConfig); // The generated props config will match the factory name.

usageExample() => (Foo()..items = ['bar'])();

Accessing and manipulating props / state within UiComponent2

Within the UiComponent2 class, props and state are not just Maps. They are instances of UiProps and UiState, which means you don’t need String keys to access them!
newProps() and newState() are also exposed to conveniently create empty instances of UiProps and UiState as needed.
typedPropsFactory() and typedStateFactory() are also exposed to conveniently create typed props / state objects out of any provided backing map.

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooProps on UiProps {
  late String color;
  Function()? onDidActivate;
  Function()? onDidDeactivate;
}
mixin FooState on UiState {
  late bool isActive;
}

class FooComponent extends UiStatefulComponent2<FooProps, FooState> {
  @override
  Map get defaultProps => (newProps()
    ..color = '#66cc00'
  );

  @override
  Map get initialState => (newState()
    ..isActive = false
  );

  @override
  void componentDidUpdate(Map prevProps, Map prevState, [dynamic snapshot]) {
    var tPrevState = typedStateFactory(prevState);
    var tPrevProps = typedPropsFactory(prevProps);

    if (state.isActive && !tPrevState.isActive) {
      props.onDidActivate?.call();
    } else if (!state.isActive && tPrevState.isActive) {
      props.onDidDeactivate?.call();
    }
  }

  @override
  dynamic render() {
    return (Dom.div()
      ..modifyProps(addUnconsumedDomProps)
      ..style = {
        ...newStyleFromProps(props),
        'color': props.color,
        'fontWeight': state.isActive ? 'bold' : 'normal', 
      }
    )(
      (Dom.button()..onClick = _handleButtonClick)('Toggle'),
      props.children,
    );
  }

  void _handleButtonClick(SyntheticMouseEvent event) {
    setState(newState()
      ..isActive = !state.isActive
    );
  }
}

Fluent-style component consumption

The OverReact analyzer plugin has many lints and assists to make authoring OverReact components easier!

In OverReact, components are consumed by invoking a UiFactory to return a new UiProps builder, which is then modified and invoked to build a ReactElement.

This is done to make "fluent-style" component consumption possible, so that the OverReact consumer experience is very similar to the React JS / "vanilla" react-dart experience.

To demonstrate the similarities, the example below shows a render method for JS, JSX, react-dart, and over_react that will have the exact same HTML markup result.

React JS:

render() {
  return React.createElement('div', {className: 'container'},
    React.createElement('h1', null, 'Click the button!'),
    React.createElement('button', {
      id: 'main_button',
      onClick: _handleClick
    }, 'Click me')
  );
}

React JS (JSX):

render() {
  return <div className="container">
    <h1>Click the button!</h1>
    <button
      id="main_button"
      onClick={_handleClick}
    >Click me</button>
  </div>;
}

Vanilla react-dart:

render() {
  return react.div({'className': 'container'},
    react.h1({}, 'Click the button!'),
    react.button({
      'id': 'main_button',
      'onClick': _handleClick
    }, 'Click me')
  );
}

OverReact:

render() {
  return (Dom.div()..className = 'container')(
    Dom.h1()('Click the button!'),
    (Dom.button()
      ..id = 'main_button'
      ..onClick = _handleClick
    )('Click me')
  );
}

Let’s break down the OverReact fluent-style shown above

render() {
  // Create a builder for a <div>,
  // add a CSS class name by cascading a typed setter,
  // and invoke the builder with the HTML DOM <h1> and <button> children.
  return (Dom.div()..className = 'container')(

    // Create a builder for an <h1> and invoke it with children.
    // No need for wrapping parentheses, since no props are added.
    Dom.h1()('Click the button!'),

    // Create a builder for a <button>,
    (Dom.button()
      // add a ubiquitous DOM prop exposed on all components,
      // which Dom.button() forwards to its rendered DOM,
      ..id = 'main_button'
      // add another prop,
      ..onClick = _handleClick
    // and finally invoke the builder with children.
    )('Click me')
  );
}

DOM components and props

All react-dart DOM components (react.div, react.a, etc.) have a corresponding Dom method (Dom.div(), Dom.a(), etc.) in OverReact.

ReactElement renderLink() {
  return (Dom.a()
    ..id = 'home_link'
    ..href = '/home'
  )('Home');
}

ReactElement renderResizeHandle() {
  return (Dom.div()
    ..className = 'resize-handle'
    ..onMouseDown = _startDrag
  )();
}

OverReact DOM components return a new DomProps builder, which can be used to render them via our fluent interface as shown in the examples above.
- DomProps has statically-typed getters and setters for all HTML attribute props.
- The domProps() function is also available to create a new typed Map or a typed view into an existing Map. Useful for manipulating DOM props and adding DOM props to components that don’t forward them directly, or to access a DOM prop from a plain map in a lifecycle method as shown below.
```
@override
void componentDidUpdate(Map prevProps, Map prevState, [dynamic snapshot]) {
  // Say you want to compare the previous / current value of `DomProps.title` here...
  final titleChanged = domProps(prevProps).title != props.title;
}
```

Component Formatting

A note on dart_style:

Currently, dart_style (dartfmt) decreases the readability of components built using OverReact's fluent-style. See dart-lang/dart_style#549 for more info.

We're exploring some different ideas to improve automated formatting, but for the time being, we do not recommend using dart_style with OverReact.

However, if you do choose to use dart_style, you can greatly improve its output by using trailing commas in children argument lists:

dart_style formatting:
return (Button()
  ..id = 'flip'
  ..skin =
      ButtonSkin.vanilla)((Dom.span()
  ..className = 'flip-container')((Dom.span()..className = 'flipper')(
    (Dom.span()
      ..className =
          'front-side')((Icon()..glyph = IconGlyph.CHEVRON_DOUBLE_RIGHT)()),
    (Dom.span()
      ..className =
          'back-side')((Icon()..glyph = IconGlyph.CHEVRON_DOUBLE_LEFT)()))));
dart_style formatting, when trailing commas are used:
return (Button()
  ..id = 'flip'
  ..skin = ButtonSkin.vanilla)(
  (Dom.span()..className = 'flip-container')(
    (Dom.span()..className = 'flipper')(
      (Dom.span()..className = 'front-side')(
        (Icon()..glyph = IconGlyph.CHEVRON_DOUBLE_RIGHT)(),
      ),
      (Dom.span()..className = 'back-side')(
        (Icon()..glyph = IconGlyph.CHEVRON_DOUBLE_LEFT)(),
      ),
    ),
  ),
);

Guidelines

To help ensure your OverReact code is readable and consistent, we've arrived at the following formatting rules.

ALWAYS place the closing builder parent on a new line.

Good:

(Button()
  ..skin = ButtonSkin.SUCCESS
  ..isDisabled = true
)('Submit')

Bad:

(Button()
  ..skin = ButtonSkin.SUCCESS
  ..isDisabled = true)('Submit')

ALWAYS pass component children on a new line with trailing commas and 2 space indentation.

Good:

Dom.div()(
  Dom.span()('nested component'),
)

Dom.div()(
  Dom.span()('nested component A'),
  Dom.span()('nested component B'),
)

Bad:

// Children are not on a new line; in most cases,
// this makes it difficult to quickly determine nesting.
Dom.div()(Dom.span()('nested component'), Dom.span()('nested component'))

// With nested hierarchies, continuation indents can quickly result
// in a "pyramid of Doom"
Dom.div()(
    Dom.ul()(
        Dom.li()(
            Dom.a()('A link!')
        )
    )
)

// Omitting trailing commas makes it a pain to rearrange lines
Dom.div()(
  Dom.span()('nested component A'),
  Dom.span()('nested component B')
)
Dom.div()(
  Dom.span()('nested component B') // ugh, need to add a comma here...
  Dom.span()('nested component A'),
)

AVOID passing children within lists; lists should only be used when the number/order of the children are dynamic.

Good:

Dom.div()(
  Dom.span()('nested component'),
  Dom.span()('nested component'),
)

var children = [
  Dom.div()('List of Items:'),
]..addAll(props.items.map(renderItem));

return Dom.div()(children)

Bad:

Dom.div()([
  (Dom.span()..key = 'span1')('nested component'),
  (Dom.span()..key = 'span2')('nested component'),
])

AVOID specifying more than one cascading prop setter on the same line.

Good:

(Dom.div()
  ..id = 'my_div'
  ..className = 'my-class'
)()

Bad:

(Dom.div()..id = 'my_div'..className = 'my-class')()

Building custom components

Now that we’ve gone over how to use the over_react package in your project, the anatomy of a component and the DOM components that you get for free from OverReact, you're ready to start building your own custom React UI components.

Start with one of the component boilerplate templates below (Or, use OverReact's code snippets for WebStorm/IntelliJ and VsCode).

Component (props only)
Stateful Component (props + state)

Fill in your props and rendering/lifecycle logic.
Consume your component with the fluent interface.
Run the app you’ve set up to consume over_react
```
$ webdev serve
```
That’s it! Code will be automatically generated on the fly by the builder!

Check out some custom component demos to get a feel for what’s possible!

Component Boilerplate Templates

WebStorm/IntelliJ and VsCode Snippets

Component Boilerplate

import 'package:over_react/over_react.dart';
part 'foo_component.over_react.g.dart';

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooProps on UiProps {
  // Props go here, declared as fields:
  late bool isDisabled;
  late Iterable<String> items;
}

class FooComponent extends UiComponent2<FooProps> {
  @override
  Map get defaultProps => (newProps()
    // Cascade default props here
    ..isDisabled = false
    ..items = []
  );

  @override
  dynamic render() {
    // Return the rendered component contents here.
    // The `props` variable is typed; no need for string keys!
  }
}

Stateful Component Boilerplate

import 'package:over_react/over_react.dart';
part 'foo_component.over_react.g.dart';

UiFactory<BarProps> Bar = castUiFactory(_$Bar); // ignore: undefined_identifier

mixin BarProps on UiProps {
  // Props go here, declared as fields:
  late bool isDisabled;
  late Iterable<String> items;
}

mixin BarState on UiState {
  // State goes here, declared as fields:
  late bool isShown;
}

class BarComponent extends UiStatefulComponent2<BarProps, BarState> {
  @override
  Map get defaultProps => (newProps()
    // Cascade default props here
    ..isDisabled = false
    ..items = []
  );

  @override
  Map get initialState => (newState()
    // Cascade initial state here
    ..isShown = true
  );

  @override
  dynamic render() {
    // Return the rendered component contents here.
    // The `props` variable is typed; no need for string keys!
  }
}

Function Component Boilerplate

import 'package:over_react/over_react.dart';
part 'foo_component.over_react.g.dart';

UiFactory<FooProps> Foo = uiFunction(
  (props) {
    // Set default props using null-aware operators.
    final isDisabled = props.isDisabled ?? false;
    final items = props.items ?? [];

    // Return the rendered component contents here.
    // The `props` variable is typed; no need for string keys!
    return Fragment()(
      Dom.div()(items),
      (Dom.button()..disabled = isDisabled)('Click me!'),
    );
  },
  // The generated props config will match the factory name.
  _$FooConfig, // ignore: undefined_identifier
);

mixin FooProps on UiProps {
  // Props go here, declared as fields:
  bool? isDisabled;
  Iterable<String>? items;
}

Component Best Practices

ALWAYS write informative comments for your component factories. Include what the component relates to, relies on, or if it extends another component.

Good:

/// Use the `DropdownButton` component to render a button
/// that controls the visibility of a child [DropdownMenu].
///
/// * Related to [Button].
/// * Extends [DropdownTrigger].
/// * Similar to [SplitButton].
///
/// See: <https://link-to-any-relevant-documentation>.
UiFactory<DropdownButtonProps> DropdownButton = castUiFactory(_$DropdownButton); // ignore: undefined_identifier

Bad:

/// Component Factory for a dropdown button component.
UiFactory<DropdownButtonProps> DropdownButton = castUiFactory(_$DropdownButton); // ignore: undefined_identifier

ALWAYS set a default / initial value for boolean props / state fields, and document that value in a comment.

Why? Without default prop values for bool fields, they could be null - which is extremely confusing and can lead to a lot of unnecessary null-checking in your business logic.

Good:

mixin DropdownButtonProps on UiProps {
  /// Whether the [DropdownButton] appears disabled.
  ///
  /// Default: `false`
  bool isDisabled;

  /// Whether the [DropdownButton]'s child [DropdownMenu] is open
  /// when the component is first mounted.
  ///
  /// Determines the initial value of [DropdownButtonState.isOpen].
  ///
  /// Default: `false`
  bool initiallyOpen;
}

mixin DropdownButtonState on UiState {
  /// Whether the [DropdownButton]'s child [DropdownMenu] is open.
  ///
  /// Initial: [DropdownButtonProps.initiallyOpen]
  bool isOpen;
}

DropdownButtonComponent
    extends UiStatefulComponent2<DropdownButtonProps, DropdownButtonState> {
  @override
  Map get defaultProps => (newProps()
    ..isDisabled = false
    ..initiallyOpen = false
  );

  @override
  Map get initialState => (newState()
    ..isOpen = props.initiallyOpen
  );
}

Bad:

mixin DropdownButtonProps on UiProps {
  bool isDisabled;
  bool initiallyOpen;
}

mixin DropdownButtonState on UiState {
  bool isOpen;
}

DropdownButtonComponent
    extends UiStatefulComponent2<DropdownButtonProps, DropdownButtonState> {
  // Confusing stuff is gonna happen in here with
  // bool props that could be null.
}

AVOID adding props or state fields that don't have an informative comment.

Good:

mixin DropdownButtonProps on UiProps {
  /// Whether the [DropdownButton] appears disabled.
  ///
  /// Default: `false`
  bool isDisabled;

  /// Whether the [DropdownButton]'s child [DropdownMenu] is open
  /// when the component is first mounted.
  ///
  /// Determines the initial value of [DropdownButtonState.isOpen].
  ///
  /// Default: `false`
  bool initiallyOpen;
}

mixin DropdownButtonState on UiState {
  /// Whether the [DropdownButton]'s child [DropdownMenu] is open.
  ///
  /// Initial: [DropdownButtonProps.initiallyOpen]
  bool isOpen;
}

Bad:

mixin DropdownButtonProps on UiProps {
  bool isDisabled;
  bool initiallyOpen;
}

mixin DropdownButtonState on UiState {
  bool isOpen;
}

Ignore Ungenerated Warnings Project-Wide

To avoid having to add // ignore: uri_has_not_been_generated to each component library on the part/import that references generated code, ignore this warning globally within analysis_options.yaml:

 analyzer:
   errors:
     uri_has_not_been_generated: ignore

Alternatively, include workiva_analysis_options which ignores this warning by default.

Contributing

Yes please! (Please read our contributor guidelines first)

Versioning

The over_react library adheres to Semantic Versioning:

Any API changes that are not backwards compatible will bump the major version (and reset the minor / patch).
Any new functionality that is added in a backwards-compatible manner will bump the minor version (and reset the patch).
Any backwards-compatible bug fixes that are added will bump the patch version.

OverReact

A library for building statically-typed React UI components using Dart.

This library also exposes OverReact Redux, which has its own documentation.

Migration Guides
Using OverReact
- Running tests in your project
  - OverReact Component Unit Test Examples
Anatomy of an OverReact component
Fluent-style component consumption
DOM components and props
Component Formatting
Building custom components
- Component Boilerplates
- Component Best Practices
Contributing

Migration Guides

Null safety

over_react 5.0.0 introduces support for null safety.

Now, you can declare non-nullable required props, using the late keyword. See the docs null safety and required props for more information.

To migrate components to null safety, see our null safety migration guide.

More Migration Guides

New component boilerplate: How to update to the mixin-based (mixin MyProps on UiProps {}) over_react component declaration syntax.
UiComponent2: How to move off the deprecated UiComponent base class and onto UiComponent2.
BuiltRedux to Redux: How to transition to OverReact Redux from BuiltRedux.
Flux to Redux: A guide to how to transition from w_flux to OverReact Redux. This guide also introduces a new architecture, Influx, that can be used for incremental refactors.
Dart2 Migration: Documentation on the Dart 2 builder updates and how to transition componentry to Dart 2.

Using OverReact

Prerequisites

Familiarize yourself with React JS

Since OverReact is built atop React JS, we strongly encourage you to gain familiarity with it by reading some React JS tutorials first.

Familiarize yourself with Dart Web applications

If you have never built a Web application in Dart, we strongly encourage you to gain familiarity with the core terminology, tools and boilerplate necessary to serve an application locally using Dart. Dart has fantastic documentation and tutorials to get you started.

Add the over_react package as a dependency in your pubspec.yaml.
```
dependencies:
  over_react: ^4.0.0
```
Enable the OverReact Analyzer Plugin (beta), which has many lints and assists to make authoring OverReact components easier!

<html>
  <head>
    <!-- ... -->
  </head>
  <body>
    <div id="react_mount_point">
      // OverReact component render() output will show up here.
    </div>

    <script src="packages/react/js/react.dev.js"></script>

    <!-- NOTE: "index" should correspond to the
         name of the `.dart` file that contains your `main()` entrypoint. -->
    <script type="application/javascript" defer src="index.dart.js"></script>
  </body>
</html>

Note: When serving your application in production, use packages/react/js/react.min.js file instead of the un-minified packages/react/js/react.dev.js file shown in the example above.

Be sure to namespace the react_dom.dart import as react_dom to avoid collisions with UiComponent.render when creating custom components.

import 'dart:html';
import 'package:over_react/react_dom.dart' as react_dom;
import 'package:over_react/over_react.dart';

// Example of where the `Foo` component might be exported from
import 'package:your_package_name/foo.dart';

main() {
  // Mount / render your component/application.
  react_dom.render(
    Foo()(),
    querySelector('#react_mount_point'),
  );
}

Run webdev serve in the root of your Dart project.

Note: If you're not using the latest component boilerplate, you'll have to restart your analysis server in your IDE for the built types to resolve properly after the build completes. Unfortunately, this is a known limitation in the analysis server at this time.

Migrate your components to the latest component boilerplate to never worry about this again!

Running unit tests in your project

When running unit tests on code that uses the over_react builder (or any code that imports over_react), you must run your tests using the build_runner package.

Warning: Do not run tests via pub run build_runner test in a package while another instance of build_runner (e.g. pub run build_runner serve) is running in that same package. This workflow is unsupported by build_runner

Run tests using the build_runner package, and specify the platform to be a browser platform. Example:
```
$ pub run build_runner test -- -p chrome test/your_test_file.dart
```

OverReact Component Unit Test Examples

Below are links to a UI component from our example "Todo App", and its analogous tests that we've written for components we use in . We utilize the utilities found in our over_react_test library.

TodoListItem

Anatomy of an OverReact component

If you are not familiar with React JS

Since OverReact is built atop React JS, we strongly encourage you to gain familiarity with it by reading this React JS tutorial first.

The over_react library functions as an additional "layer" atop the Dart react package which handles the underlying JS interop that wraps around React JS.

UiFactory
UiProps
component, either a:
1. function component uiFunction
2. class component UiComponent2 (and optionally a UiState)

UiFactory

UiFactory is a function that returns a new instance of a component's UiProps class.

// Class component
UiFactory<FooProps> Foo = castUiFactory(_$Foo);

// Function component
UiFactory<FooProps> Foo = uiFunction((props) { /*...*/ }, _$FooConfig);

This factory is the entry-point to consuming any OverReact component.
The UiProps instance it returns can be used as a component builder, or as a typed view into an existing props map.
castUiFactory is necessary to prevent implicit cast analysis warnings before code generation has been run.

UiProps

UiProps is a Map class that adds statically-typed getters and setters for each React component prop. It can also be invoked as a function, serving as a builder for its analogous component.

mixin FooProps on UiProps {
  // ... the props for your component go here
  String? bar;
  bool? baz;
  List<int>? bizzles;
}

- Note: The builder generates a class with getters and setters overriding the fields you declare in your mixin, but you don't need to worry about that generated class. To use props from another mixin, simply mix it in! See "With other mixins" below for more information.

With other mixins

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooPropsMixin on UiProps {
  String? bar;
  bool? baz;
  List<int>? bizzles;
}

class FooProps = UiProps with FooPropsMixin, BarPropsMixin;

class FooComponent extends UiComponent2<FooProps> {
  // ...
}

Composition

Check out an example of props mixin component composition here

UiProps as a Map

Warning

Directly reading late required props on arbitrary maps is unsafe.

See the docs on Unsafe Required Prop Reads for more information and for instructions on how to read these props safely.

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooProps on UiProps {
  String? color;
}

class FooComponent extends UiComponent2<FooProps> {
  // ...
}

void bar() {
  FooProps props = Foo();

  props.color = '#66cc00';

  print(props.color); // #66cc00
  print(props);       // {FooProps.color: #66cc00}
}

/// You can also use the factory to create a UiProps instance
/// backed by an existing Map.
void baz() {
  Map existingMap = {'FooProps.color': '#0094ff'};

  FooProps props = Foo(existingMap);

  print(props.color); // #0094ff
}

UiProps as a builder

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooProps on UiProps {
  String? color;
}

class FooComponent extends UiComponent2<FooProps> {
  ReactElement bar() {
    // Create a UiProps instance to serve as a builder
    FooProps builder = Foo();

    // Set some prop values
    builder
      ..id = 'the_best_foo'
      ..color = '#ee2724';

    // Invoke as a function with the desired children
    // to return a new instance of the component.
    return builder('child1', 'child2');
  }

  /// Even better... do it inline! (a.k.a fluent)
  ReactElement baz() {
    return (Foo()
      ..id = 'the_best_foo'
      ..color = 'red'
    )(
      'child1',
      'child2'
    );
  }
}

See fluent-style component consumption for more examples on builder usage.

UiState

UiState is a Map class (just like UiProps) that adds statically-typed getters and setters for each React component state property in a class component.

mixin FooState on UiState {
  // ...
}

UiState is optional, and won’t be used for every component. Check out the UiStatefulComponent boilerplate for more information.

Note: The builder will make the concrete getters and setters available from the mixin fields you author in a generated class. To mix state classes together, the mixin class should be used rather than the generated props class. See "With other mixins" above for more information.

UiComponent2 (class-based components)

For guidance on updating to UiComponent2 from UiComponent, check out the UiComponent2 Migration Guide.

UiComponent2 is a subclass of react.Component2, containing lifecycle methods and rendering logic for components.

class FooComponent extends UiComponent2<FooProps> {
  // ...
}

This class provides statically-typed props via UiProps, as well as utilities for prop forwarding and CSS class merging.
The UiStatefulComponent2 flavor augments UiComponent2 behavior with statically-typed state via UiState.

uiFunction (function components)

uiFunction lets you declare a function component.

In JavaScript, function components are just plain functions, but in over_react this wrapper is needed to perform JS interop and wire up the typed props class.

mixin FooProps on UiProps {
  bool? isDisabled;
  List? items;
}

UiFactory<FooProps> Foo = uiFunction((props) {
  // Set default props using null-aware operators.
  final isDisabled = props.isDisabled ?? false;
  final items = props.items ?? [];

  // Return the rendered component contents here.
  return Fragment()(
    Dom.div()(items),
    (Dom.button()..disabled = isDisabled)('Click me!'),
  );
}, _$FooConfig); // The generated props config will match the factory name.

usageExample() => (Foo()..items = ['bar'])();

Accessing and manipulating props / state within UiComponent2

Within the UiComponent2 class, props and state are not just Maps. They are instances of UiProps and UiState, which means you don’t need String keys to access them!
newProps() and newState() are also exposed to conveniently create empty instances of UiProps and UiState as needed.
typedPropsFactory() and typedStateFactory() are also exposed to conveniently create typed props / state objects out of any provided backing map.

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooProps on UiProps {
  late String color;
  Function()? onDidActivate;
  Function()? onDidDeactivate;
}
mixin FooState on UiState {
  late bool isActive;
}

class FooComponent extends UiStatefulComponent2<FooProps, FooState> {
  @override
  Map get defaultProps => (newProps()
    ..color = '#66cc00'
  );

  @override
  Map get initialState => (newState()
    ..isActive = false
  );

  @override
  void componentDidUpdate(Map prevProps, Map prevState, [dynamic snapshot]) {
    var tPrevState = typedStateFactory(prevState);
    var tPrevProps = typedPropsFactory(prevProps);

    if (state.isActive && !tPrevState.isActive) {
      props.onDidActivate?.call();
    } else if (!state.isActive && tPrevState.isActive) {
      props.onDidDeactivate?.call();
    }
  }

  @override
  dynamic render() {
    return (Dom.div()
      ..modifyProps(addUnconsumedDomProps)
      ..style = {
        ...newStyleFromProps(props),
        'color': props.color,
        'fontWeight': state.isActive ? 'bold' : 'normal', 
      }
    )(
      (Dom.button()..onClick = _handleButtonClick)('Toggle'),
      props.children,
    );
  }

  void _handleButtonClick(SyntheticMouseEvent event) {
    setState(newState()
      ..isActive = !state.isActive
    );
  }
}

Fluent-style component consumption

The OverReact analyzer plugin has many lints and assists to make authoring OverReact components easier!

In OverReact, components are consumed by invoking a UiFactory to return a new UiProps builder, which is then modified and invoked to build a ReactElement.

This is done to make "fluent-style" component consumption possible, so that the OverReact consumer experience is very similar to the React JS / "vanilla" react-dart experience.

To demonstrate the similarities, the example below shows a render method for JS, JSX, react-dart, and over_react that will have the exact same HTML markup result.

React JS:

render() {
  return React.createElement('div', {className: 'container'},
    React.createElement('h1', null, 'Click the button!'),
    React.createElement('button', {
      id: 'main_button',
      onClick: _handleClick
    }, 'Click me')
  );
}

React JS (JSX):

render() {
  return <div className="container">
    <h1>Click the button!</h1>
    <button
      id="main_button"
      onClick={_handleClick}
    >Click me</button>
  </div>;
}

Vanilla react-dart:

render() {
  return react.div({'className': 'container'},
    react.h1({}, 'Click the button!'),
    react.button({
      'id': 'main_button',
      'onClick': _handleClick
    }, 'Click me')
  );
}

OverReact:

render() {
  return (Dom.div()..className = 'container')(
    Dom.h1()('Click the button!'),
    (Dom.button()
      ..id = 'main_button'
      ..onClick = _handleClick
    )('Click me')
  );
}

Let’s break down the OverReact fluent-style shown above

render() {
  // Create a builder for a <div>,
  // add a CSS class name by cascading a typed setter,
  // and invoke the builder with the HTML DOM <h1> and <button> children.
  return (Dom.div()..className = 'container')(

    // Create a builder for an <h1> and invoke it with children.
    // No need for wrapping parentheses, since no props are added.
    Dom.h1()('Click the button!'),

    // Create a builder for a <button>,
    (Dom.button()
      // add a ubiquitous DOM prop exposed on all components,
      // which Dom.button() forwards to its rendered DOM,
      ..id = 'main_button'
      // add another prop,
      ..onClick = _handleClick
    // and finally invoke the builder with children.
    )('Click me')
  );
}

DOM components and props

All react-dart DOM components (react.div, react.a, etc.) have a corresponding Dom method (Dom.div(), Dom.a(), etc.) in OverReact.

ReactElement renderLink() {
  return (Dom.a()
    ..id = 'home_link'
    ..href = '/home'
  )('Home');
}

ReactElement renderResizeHandle() {
  return (Dom.div()
    ..className = 'resize-handle'
    ..onMouseDown = _startDrag
  )();
}

OverReact DOM components return a new DomProps builder, which can be used to render them via our fluent interface as shown in the examples above.
- DomProps has statically-typed getters and setters for all HTML attribute props.
- The domProps() function is also available to create a new typed Map or a typed view into an existing Map. Useful for manipulating DOM props and adding DOM props to components that don’t forward them directly, or to access a DOM prop from a plain map in a lifecycle method as shown below.
```
@override
void componentDidUpdate(Map prevProps, Map prevState, [dynamic snapshot]) {
  // Say you want to compare the previous / current value of `DomProps.title` here...
  final titleChanged = domProps(prevProps).title != props.title;
}
```

Component Formatting

A note on dart_style:

Currently, dart_style (dartfmt) decreases the readability of components built using OverReact's fluent-style. See dart-lang/dart_style#549 for more info.

We're exploring some different ideas to improve automated formatting, but for the time being, we do not recommend using dart_style with OverReact.

However, if you do choose to use dart_style, you can greatly improve its output by using trailing commas in children argument lists:

dart_style formatting:
return (Button()
  ..id = 'flip'
  ..skin =
      ButtonSkin.vanilla)((Dom.span()
  ..className = 'flip-container')((Dom.span()..className = 'flipper')(
    (Dom.span()
      ..className =
          'front-side')((Icon()..glyph = IconGlyph.CHEVRON_DOUBLE_RIGHT)()),
    (Dom.span()
      ..className =
          'back-side')((Icon()..glyph = IconGlyph.CHEVRON_DOUBLE_LEFT)()))));
dart_style formatting, when trailing commas are used:
return (Button()
  ..id = 'flip'
  ..skin = ButtonSkin.vanilla)(
  (Dom.span()..className = 'flip-container')(
    (Dom.span()..className = 'flipper')(
      (Dom.span()..className = 'front-side')(
        (Icon()..glyph = IconGlyph.CHEVRON_DOUBLE_RIGHT)(),
      ),
      (Dom.span()..className = 'back-side')(
        (Icon()..glyph = IconGlyph.CHEVRON_DOUBLE_LEFT)(),
      ),
    ),
  ),
);

Guidelines

To help ensure your OverReact code is readable and consistent, we've arrived at the following formatting rules.

ALWAYS place the closing builder parent on a new line.

Good:

(Button()
  ..skin = ButtonSkin.SUCCESS
  ..isDisabled = true
)('Submit')

Bad:

(Button()
  ..skin = ButtonSkin.SUCCESS
  ..isDisabled = true)('Submit')

ALWAYS pass component children on a new line with trailing commas and 2 space indentation.

Good:

Dom.div()(
  Dom.span()('nested component'),
)

Dom.div()(
  Dom.span()('nested component A'),
  Dom.span()('nested component B'),
)

Bad:

// Children are not on a new line; in most cases,
// this makes it difficult to quickly determine nesting.
Dom.div()(Dom.span()('nested component'), Dom.span()('nested component'))

// With nested hierarchies, continuation indents can quickly result
// in a "pyramid of Doom"
Dom.div()(
    Dom.ul()(
        Dom.li()(
            Dom.a()('A link!')
        )
    )
)

// Omitting trailing commas makes it a pain to rearrange lines
Dom.div()(
  Dom.span()('nested component A'),
  Dom.span()('nested component B')
)
Dom.div()(
  Dom.span()('nested component B') // ugh, need to add a comma here...
  Dom.span()('nested component A'),
)

AVOID passing children within lists; lists should only be used when the number/order of the children are dynamic.

Good:

Dom.div()(
  Dom.span()('nested component'),
  Dom.span()('nested component'),
)

var children = [
  Dom.div()('List of Items:'),
]..addAll(props.items.map(renderItem));

return Dom.div()(children)

Bad:

Dom.div()([
  (Dom.span()..key = 'span1')('nested component'),
  (Dom.span()..key = 'span2')('nested component'),
])

AVOID specifying more than one cascading prop setter on the same line.

Good:

(Dom.div()
  ..id = 'my_div'
  ..className = 'my-class'
)()

Bad:

(Dom.div()..id = 'my_div'..className = 'my-class')()

Building custom components

Start with one of the component boilerplate templates below (Or, use OverReact's code snippets for WebStorm/IntelliJ and VsCode).

Component (props only)
Stateful Component (props + state)

Fill in your props and rendering/lifecycle logic.
Consume your component with the fluent interface.
Run the app you’ve set up to consume over_react
```
$ webdev serve
```
That’s it! Code will be automatically generated on the fly by the builder!

Check out some custom component demos to get a feel for what’s possible!

Component Boilerplate Templates

WebStorm/IntelliJ and VsCode Snippets

Component Boilerplate

import 'package:over_react/over_react.dart';
part 'foo_component.over_react.g.dart';

UiFactory<FooProps> Foo = castUiFactory(_$Foo); // ignore: undefined_identifier

mixin FooProps on UiProps {
  // Props go here, declared as fields:
  late bool isDisabled;
  late Iterable<String> items;
}

class FooComponent extends UiComponent2<FooProps> {
  @override
  Map get defaultProps => (newProps()
    // Cascade default props here
    ..isDisabled = false
    ..items = []
  );

  @override
  dynamic render() {
    // Return the rendered component contents here.
    // The `props` variable is typed; no need for string keys!
  }
}

Stateful Component Boilerplate

import 'package:over_react/over_react.dart';
part 'foo_component.over_react.g.dart';

UiFactory<BarProps> Bar = castUiFactory(_$Bar); // ignore: undefined_identifier

mixin BarProps on UiProps {
  // Props go here, declared as fields:
  late bool isDisabled;
  late Iterable<String> items;
}

mixin BarState on UiState {
  // State goes here, declared as fields:
  late bool isShown;
}

class BarComponent extends UiStatefulComponent2<BarProps, BarState> {
  @override
  Map get defaultProps => (newProps()
    // Cascade default props here
    ..isDisabled = false
    ..items = []
  );

  @override
  Map get initialState => (newState()
    // Cascade initial state here
    ..isShown = true
  );

  @override
  dynamic render() {
    // Return the rendered component contents here.
    // The `props` variable is typed; no need for string keys!
  }
}

Function Component Boilerplate

import 'package:over_react/over_react.dart';
part 'foo_component.over_react.g.dart';

UiFactory<FooProps> Foo = uiFunction(
  (props) {
    // Set default props using null-aware operators.
    final isDisabled = props.isDisabled ?? false;
    final items = props.items ?? [];

    // Return the rendered component contents here.
    // The `props` variable is typed; no need for string keys!
    return Fragment()(
      Dom.div()(items),
      (Dom.button()..disabled = isDisabled)('Click me!'),
    );
  },
  // The generated props config will match the factory name.
  _$FooConfig, // ignore: undefined_identifier
);

mixin FooProps on UiProps {
  // Props go here, declared as fields:
  bool? isDisabled;
  Iterable<String>? items;
}

Component Best Practices

ALWAYS write informative comments for your component factories. Include what the component relates to, relies on, or if it extends another component.

Good:

/// Use the `DropdownButton` component to render a button
/// that controls the visibility of a child [DropdownMenu].
///
/// * Related to [Button].
/// * Extends [DropdownTrigger].
/// * Similar to [SplitButton].
///
/// See: <https://link-to-any-relevant-documentation>.
UiFactory<DropdownButtonProps> DropdownButton = castUiFactory(_$DropdownButton); // ignore: undefined_identifier

Bad:

/// Component Factory for a dropdown button component.
UiFactory<DropdownButtonProps> DropdownButton = castUiFactory(_$DropdownButton); // ignore: undefined_identifier

ALWAYS set a default / initial value for boolean props / state fields, and document that value in a comment.

Why? Without default prop values for bool fields, they could be null - which is extremely confusing and can lead to a lot of unnecessary null-checking in your business logic.

Good:

mixin DropdownButtonProps on UiProps {
  /// Whether the [DropdownButton] appears disabled.
  ///
  /// Default: `false`
  bool isDisabled;

  /// Whether the [DropdownButton]'s child [DropdownMenu] is open
  /// when the component is first mounted.
  ///
  /// Determines the initial value of [DropdownButtonState.isOpen].
  ///
  /// Default: `false`
  bool initiallyOpen;
}

mixin DropdownButtonState on UiState {
  /// Whether the [DropdownButton]'s child [DropdownMenu] is open.
  ///
  /// Initial: [DropdownButtonProps.initiallyOpen]
  bool isOpen;
}

DropdownButtonComponent
    extends UiStatefulComponent2<DropdownButtonProps, DropdownButtonState> {
  @override
  Map get defaultProps => (newProps()
    ..isDisabled = false
    ..initiallyOpen = false
  );

  @override
  Map get initialState => (newState()
    ..isOpen = props.initiallyOpen
  );
}

Bad:

mixin DropdownButtonProps on UiProps {
  bool isDisabled;
  bool initiallyOpen;
}

mixin DropdownButtonState on UiState {
  bool isOpen;
}

DropdownButtonComponent
    extends UiStatefulComponent2<DropdownButtonProps, DropdownButtonState> {
  // Confusing stuff is gonna happen in here with
  // bool props that could be null.
}

AVOID adding props or state fields that don't have an informative comment.

Good:

mixin DropdownButtonProps on UiProps {
  /// Whether the [DropdownButton] appears disabled.
  ///
  /// Default: `false`
  bool isDisabled;

  /// Whether the [DropdownButton]'s child [DropdownMenu] is open
  /// when the component is first mounted.
  ///
  /// Determines the initial value of [DropdownButtonState.isOpen].
  ///
  /// Default: `false`
  bool initiallyOpen;
}

mixin DropdownButtonState on UiState {
  /// Whether the [DropdownButton]'s child [DropdownMenu] is open.
  ///
  /// Initial: [DropdownButtonProps.initiallyOpen]
  bool isOpen;
}

Bad:

mixin DropdownButtonProps on UiProps {
  bool isDisabled;
  bool initiallyOpen;
}

mixin DropdownButtonState on UiState {
  bool isOpen;
}

Ignore Ungenerated Warnings Project-Wide

To avoid having to add // ignore: uri_has_not_been_generated to each component library on the part/import that references generated code, ignore this warning globally within analysis_options.yaml:

 analyzer:
   errors:
     uri_has_not_been_generated: ignore

Alternatively, include workiva_analysis_options which ignores this warning by default.

Contributing

Yes please! (Please read our contributor guidelines first)

Versioning

The over_react library adheres to Semantic Versioning:

Any API changes that are not backwards compatible will bump the major version (and reset the minor / patch).
Any new functionality that is added in a backwards-compatible manner will bump the minor version (and reset the patch).
Any backwards-compatible bug fixes that are added will bump the patch version.

Workiva/over_react(opens in a new tab)

README

OverReact

Migration Guides

Null safety

More Migration Guides

Using OverReact

Running unit tests in your project

OverReact Component Unit Test Examples

Anatomy of an OverReact component

UiFactory

UiProps

With other mixins

Composition

UiProps as a Map

UiProps as a builder

UiState

UiComponent2 (class-based components)

uiFunction (function components)

Accessing and manipulating props / state within UiComponent2

Fluent-style component consumption

DOM components and props

Component Formatting

Guidelines

Building custom components

Component Boilerplate Templates

WebStorm/IntelliJ and VsCode Snippets

Component Boilerplate

Stateful Component Boilerplate

Function Component Boilerplate

Component Best Practices

Ignore Ungenerated Warnings Project-Wide

Contributing

Versioning

README

OverReact

Migration Guides

Null safety

More Migration Guides

Using OverReact

Running unit tests in your project

OverReact Component Unit Test Examples

Anatomy of an OverReact component

UiFactory

UiProps

With other mixins

Composition

UiProps as a Map

UiProps as a builder

UiState

UiComponent2 (class-based components)

uiFunction (function components)

Accessing and manipulating props / state within UiComponent2

Fluent-style component consumption

DOM components and props

Component Formatting

Guidelines

Building custom components

Component Boilerplate Templates

WebStorm/IntelliJ and VsCode Snippets

Component Boilerplate

Stateful Component Boilerplate

Function Component Boilerplate

Component Best Practices

Ignore Ungenerated Warnings Project-Wide

Contributing

Versioning