flutter_mediator 1.0.0+1

Flutter mediator is a MVC state management package base on InheritedModel with automatic aspect management to make them simpler, easier, and intuitive to use.

Flutter Mediator

Flutter mediator is a MVC state management package base on InheritedModel with automatic aspect management to make them simpler, easier, and intuitive to use.

Features

• Easy and simple to use - automatically make things work by only a few steps
• Efficiency and Performance - use InheritedModel as the underlying layer to make the app quick response
• Lightweight - small package size
• Flexible - provide both automatic and manual observation
• Intuitive - three main classes: Publisher, Subscriber, Host
  Publisher - publish aspects
    Subscriber - subscribe aspects
    Host - dispatch aspects

Flutter Widget of the Week: InheritedModel explained

InheritedModel provides an aspect parameter to its descendants to indicate which fields they care about to determine whether that widget needs to rebuild. InheritedModel can help you rebuild its descendants only when necessary.

Setting up

Add the following dependency to pubspec.yaml of your flutter project:

dependencies:
  flutter_mediator: "^1.0.0+1"

Import flutter_mediator in files that will be used:

import 'package:flutter_mediator/mediator.dart';

For help getting started with Flutter, view the online documentation.

Getting Started Quick Steps

Model, View, Controller, Host:

Model:

1. Extend the model from Publisher
2. Declare rx variables with .rx, which will automatically rebuild the aspect-related-widget when updated.
3. Implement the update methods.

MyModel.dart

class MyModel extends Publisher {
  /// `.rx` make the var automatically rebuild the aspect-related-widget when updated
  var int1 =  0.rx;

  void updateInt1() {
    /// since int1 is a rx variable,
    /// it will automatically rebuild the aspect-realted-widget when updated
    int1 +=  1;
  }

Subscribe the View:

4. Subscribe the widget with designated one or more aspect.
   4-1. Choice an aspect to represent the widget.
       In this example, a string type aspect with value 'int1' is designated.
   4-2. Designate the model to be used.
       In this example, myModel of class <MyModel> is used.
   _Then any rx variables used inside the create method will automatically rebuild the aspect-related-widget when updated._ (triggered by getter and setter)

class Int1Listener extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return 'int1'.subModel<MyModel>(
      create: (context, model) {
        /// Since model.int1 is a rx variable,
        /// it will automatically rebuild the aspect-related-widget when updated.
        /// In this example, the aspect is 'int1' of <MyModel>.
        return  Text('Int1 is ${model.int1}');
      },
    );
  }
}

Controller:

5. Put the controller somewhere in the widget tree.
   For example, get the model of class <MyModel> and execute it's update method within a RaisedButton.

RaisedButton(
  child: const Text('Update Int1'),
  onPressed: () => context.getModel<MyModel>().updateInt1(),
);

Host:

6. Inject host at the top level of the widget tree.

void  main() {
  runApp(
    MultiHost.create2(
      MyModel(updateMs:  1000), // model extends from Publisher
      ListModel(updateMs:  500),// model extends from Publisher
      child:  MyApp(),
    ),
  /// MultiHost.create1 to MultiHost.create9 are provided by the package.
  );
}

Works automatically!

7. Then the state works automatically!

These steps can help you with most situations. The following details will explain the package one step further.

Example

You can find the example in the example folder.
Try it once, you will see it's simple and easy to use.

Detail

1. Single model - host
2. Multiple models - host
3. Automatically update the widget with rx variable - Publisher
4. Access the underlying value directly of rx variable - Publisher
5. Update the value by call style of rx variable - Publisher
6. Manually publish an aspect of the model - Publisher
7. Manually publish multiple aspects of the model - Publisher
8. Manually publish all aspects of the model - Publisher
9. Future publish of the model - Publisher
10. Rebuild only once per frame for the same aspect - Publisher
11. Writing model helper - Publisher
12. Get the model - Subscriber
13. Subscribe an aspect of the model - Subscriber
14. Subscribe multiple aspects of the model - Subscriber
15. Subscribe all aspects of the model - Subscriber
16. Subscribe with enum aspects of the model - Subscriber
17. Manage rx aspects - Chain react aspects - advance topic
18. Implement custom rx class - advance topic
19. Aspect type - terminology

1. Single model

void main() {
  runApp(
    Host(
      model: AppModel(), // model extends from Publisher
      child: MyApp(),
    ),
  );
}

back to detail

2. Multiple models

MultiHost.create1 to MultiHost.create9 are provided by the package.
You can add more MultiHost.createXX method, see multi_host.dart for example.

void main() {
  runApp(
    MultiHost.create2(
      MyModel(updateMs: 1000),  // model extends from Publisher
      ListModel(updateMs: 500), // model extends from Publisher
      child:  MyApp(),
    ),
  );
}

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3. Automatically update the widget

.rx make the var automatically rebuild the aspect-related-widget when updated

int:

class MyModel extends Publisher {
/// `.rx` make the var automatically update the aspect-related-widget
var int1 = 0.rx;

void  updateInt1() {
  int1 += 1; // automatically update the aspect-related-widget
}

List:

class ListModel extends Publisher {
  /// `.rx` make the var automatically update the aspect-related-widget
  final data =  <ListItem>[].rx;

  void updateListItem() {
    // get new item data...
    final newItem = ListItem(itemName, units, color);
    data.add(newItem); // automatically update the aspect-related-widget
  }

rx variable of type int, double, num, string, bool, list, map, set are provided by the package.
See also RxInt class, RxList class, RxList.add

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4. Access the underlying value directly

Access the underlying value directly by .value.

MyModel.dart

var int1 = 0.rx;
void updateInt1() {
  // int1 += 1;
  /// is the same as
  int1.value += 1; // automatically update the aspect-related-widget
}

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5. Update the value by call style

MyModel.dart

var _foo = 1.rx;
set foo(int value) {
  _foo(value); // update rx variable by call() style
  /// is the same as
  // _foo = value;
  /// is the same as
  // _foo.value = value;
}

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6. Manually publish an aspect

MyModel.dart

int manuallyInt = 0;
void manuallyPublishDemo(int value) {
  manuallyInt = value;
  publish('manuallyInt'); // manually publish aspect of 'manuallyInt'
}

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7. Manually publish multiple aspects

Putting aspects in a list to publish multiple aspects.

MyModel.dart

int _foo = 0;
int _bar = 0;
void increaseBoth() {
  _foo += 1;
  _bar += 1;
  publish(['foo', 'bar']); // manually publish multiple aspects in a list
}

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8. Manually publish all aspects

Publish null value to publish all aspects of the model.

MyModel.dart

void increaseAll() {
  //...
  publish(); // manually publish all aspects of the model
}

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9. Future publish

Use with an async method, for example,

MyModel.dart

int int1 = 0.rx;
Future<void> futureInt1() async {
  await Future.delayed(const Duration(seconds: 1));
  int1 += 1; // int1 is an rx variable, it'll automatically update the aspect-related-widget when updated
}

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10. Rebuild only once per frame

Rebuild only once per frame for the same aspect. InheritedModel use Set to accumulate aspects, thus the same aspect only cause the related widget to rebuild once.
Following code only cause the aspect-related-widget to rebuild once.

MyModel.dart

int int1 = 0.rx;
void incermentInt1() async {
  int1 += 1; // int1 is an rx variable, it'll automatically update the aspect-related-widget when updated
  publish('int1'); // manually publish 'int1'
  publish('int1'); // manually publish 'int1', again
  // only cause the aspected-related-widget to rebuild once per frame
}

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11. Writing model helper

You can write model helpers to simplified the typing, for example,

MyModel.dart - helper of MyModel

/// Helper function of MyModel
MyModel getMyModel(BuildContext context) {
  return Host.getInheritOfModel<MyModel>(context);
}

Subscriber<MyModel> subMyModel({Key key, Object aspects,
                @required CreaterOfSubscriber<MyModel> create}) {
  return aspects.subModel<MyModel>(key: key, create: create);
}

extension MyModelHelperT<T> on T {
  Subscriber<MyModel> subMyModel({Key key,
                @required CreaterOfSubscriber<MyModel> create}) {
    return Subscriber<MyModel>(key: key, aspects: this, create: create);
  }
}

ListModel.dart - helper of ListModel

/// Helper function of ListModel
ListModel getListModel(BuildContext context) {
  return Host.getInheritOfModel<ListModel>(context);
}

Subscriber<ListModel> subListModel({Key key, Object aspects,
                @required CreaterOfSubscriber<ListModel> create}) {
  return aspects.subModel<ListModel>(key: key, create: create);
}

extension ListModelHelperT<T> on T {
  Subscriber<ListModel> subListModel({Key key,
                @required CreaterOfSubscriber<ListModel> create}) {
    return Subscriber<ListModel>(key: key, aspects:  this, create: create);
  }
}

See also mediator_helper.dart for package helper.

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12. Get the model

To get the model, for example, getting MyModel,

original form

final model = Host.getInheritOfModel<MyModel>(context);

by package helper of context extension

final model = context.getModel<MyModel>();

by model helper on your own

final model = getMyModel(context);

Get current triggered frame aspects of the model. See also [e-mail].

final model = context.getModel<MyModel>();
final aspects = model.frameAspect;

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13. Subscribe an aspect

For example, listen to a String type aspect 'int1' of class <MyModel>.

original form

class Int1Listener extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Subscriber<MyModel>(
      aspects: 'int1',
      create: (context, model) {
        return Text('Int1 is ${model.int1}');
      },
    );
  }
}

with helper

class Int1Listener extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // return 'int1'.subMyModel(     // with model helper on your own
    return 'int1'.subModel<MyModel>( // with package helper
      create: (context, model) {
        return Text('Int1 is ${model.int1}');
      },
    );
  }
}

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14. Subscribe multiple aspects

Putting aspects in a list to subscribe multiple aspects.

original form

class TwoListener extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Subscriber<MyModel>(
      aspects: ['int1', 'star'],
      create: (context, model) {
        return Text('Int1 is ${model.int1} and Star is ${model.star}');
      },
    );
  }
}

with helper

class TwoListener extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // return ['int1', 'star'].subMyModel(     // with model helper on your own
    return ['int1', 'star'].subModel<MyModel>( // with package helper
      create: (context, model) {
        return Text('Int1 is ${model.int1} and Star is ${model.star}');
      },
    );
  }
}

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15. Subscribe all aspects

Provide no aspects parameter, or use null as aspect to listen to all aspects.
See also [e-mail].

original form

class AllListener extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Subscriber<MyModel>(
      // aspects: , // no aspects parameter means listen to all aspects
      create: (context, model) {
        final aspects = model.frameAspect;
        final str = aspects.isEmpty ? '' : '$aspects received';
        return Text(str);
      },
    );
  }
}

with helper

class AllListener extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // return null.subMyModel(     // with model helper on your own
    return null.subModel<MyModel>( // with package helper
      create: (context, model) {
        final aspects = model.frameAspect;
        final str = aspects.isEmpty ? '' : '$aspects received';
        return Text(str);
      },
    );
  }
}

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16. Subscribe with enum aspects

You can use enum as aspect type, for example, first, define the enum.

ListModel.dart

enum ListEnum {
  ListUpdate,
}

Then everything is the same as String type aspect, just to replace the String with enum.
See also [e-mail].

original form

class ListItemView extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Subscriber<ListModel>(
      aspects: ListEnum.ListUpdate,
      create: (context, model) {
      //...
    });
  }
}

with helper

class ListItemView extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // return  ListEnum.ListUpdate.subListModel(create: (context, model) { // with model helper on your own
    return ListEnum.ListUpdate.subModel<ListModel>(create: (context, model) { // with package helper
      //...
    });
  }
}

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17. Manage rx aspects - Chain react aspects

Chain react aspects:

Supposed you need to rebuild a widget whenever a model variable is updated, but it has nothing to do with the variable. Then you can use chain react aspects.
For example, to rebuild a widget whenever str1 of class <MyModel> is updated, and chained by the aspect 'chainStr1'.

MyModel.dart

final str1 = 's'.rx..addRxAspects('chainStr1'); // to chain react aspects

main.dart

int httpResCounter = 0;

class ChainReactListener extends StatelessWidget {
  Future<int> _futureHttpTask() async {
    await Future.delayed(const Duration(milliseconds: 0));
    return ++httpResCounter;
  }

  @override
  Widget build(BuildContext context) {
    return 'chainStr1'.subModel<MyModel>(create: (context, model) {
      return FutureBuilder(
        future: _futureHttpTask(),
        initialData: httpResCounter,
        builder: (BuildContext context, AsyncSnapshot snapshot) {
          Widget child;
          if (snapshot.hasData) {
            child = Text('str1 chain counter: $httpResCounter');
          } else {
            child = Text('str1 init counter: $httpResCounter');
          }
          return Center(child: child);
        },
      );
    });
  }
}

Then whenever str1 of class <MyModel> updates, the ChainReactListener rebuild automatically.

Manage rx aspects:

Add aspects to the rx variable:

• add an aspect: rxVar.addRxAspects('chained-aspect')
• add multiple aspects: rxVar.addRxAspects(['chained-as1', 'chained-as2'])
• add aspects from another rx variable: rxVar.addRxAspects(otherRxVar)
• broadcast to the model: rxVar.addRxAspects()

Remove aspects from the rx variable:

• remove an aspect: rxVar.removeRxAspects('chained-aspect')
• remove multiple aspects: rxVar.removeRxAspects(['chained-as1', 'chained-as2'])
• remove aspects from another rx variable: rxVar.removeRxAspects(otherRxVar)
• don't broadcast to the model: rxVar.removeRxAspects()

Retain aspects in the rx variable:

• retain an aspect: rxVar.retainRxAspects('chained-aspect')
• retain multiple aspects: rxVar.retainRxAspects(['chained-as1', 'chained-as2'])
• retain aspects from another rx variable: rxVar.retainRxAspects(otherRxVar)

Clear all rx aspects:

• rxVar.clearRxAspects()

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18. Implement custom rx class

If you need to write your own rx class, see custom_rx_class.dart for example.

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19. Aspect type

• Widget aspects - aspects that the widget subscribe with.
• Frame aspects - aspects that will be updated in this UI frame.
• Registered aspects - aspects that the model has been registered to.
• Rx aspects - aspects that the rx variables are attached. Once the rx variable gets updated, the aspects will be published.

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Changelog

Please see the Changelog page.

License

MIT