published 0.0.11

Swift Published property wrapper Dart implementation.

Motivation

Published was inspired by Published property wrapper from Swift.

There are approaches like using BloC that depend on streams and they introduce a lot of boilerplate.

Published goal is reduce that boilerplate and introduce simple state management.

How to use

Installation

To use package:published in your package, add these dependencies to your pubspec.yaml.

dependencies:
  published:

dev_dependencies:
  build_runner:
  published_gen:

Usage

import 'package:published/published.dart';

part 'counter_view_model.published.dart';

@published
abstract class CounterViewModel extends _$CounterViewModel {
  @Publisher()
  abstract int count;

  void increment() => count++;

  @override
  bool get enableLogging => true;
}

You'll have to make abstract class and annotate it with @published and extend it with _$ClassName.

Annotate abstract field for which you want to expose stream with @Publisher().

• Note: It's important to use abstract fields and classes so we can replicate Swift structs.

Then run pub run build_runner build to generate files into your source directory.

> pub run build_runner build
[INFO] ensureBuildScript: Generating build script completed, took 368ms
[INFO] BuildDefinition: Reading cached asset graph completed, took 54ms
[INFO] BuildDefinition: Checking for updates since last build completed, took 663ms
[INFO] Build: Running build completed, took 10ms
[INFO] Build: Caching finalized dependency graph completed, took 44ms
[INFO] Build: Succeeded after 4687ms with 1 outputs

NOTE: If you're using Flutter, replace pub run with flutter packages pub run.

To use it do following

 //Init
 final model = CounterViewModelBuilder.build(count: 0);
 ...

 Widget build(BuildContext context) {
   
   return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            StreamBuilder<int>(
              stream: model.$count,
              builder: (context,snapshot) => Text("${snapshot.data ?? 0}");
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => model.count++,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
 }

$classNameBuilder.build() needs to be used to create instance of the object. If you don't want to pass default value in build() use defaultValue property on Publisher like this:

@Publisher(defaultValue: "John")
abstract String name;

To observe if any property annotated with Publisher changed you can use didChange:

model.didChange.listen(() => doSomething())

If you want to enableLogging you can override getter enableLogging:

@published
abstract class CounterViewModel extends _$CounterViewModel {
  ...
  @override
  bool get enableLogging => true;
}

Finally if you want to do something on object creation you can override onBind method and place your logic there:

@published
abstract class CounterViewModel extends _$CounterViewModel {
  ...
  @override
  @override
  void onBind() {
    super.onBind();
    fetchSomeData();
  }
}