published

Description:

published

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:
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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;
}

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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
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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),
),
);
}

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$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;
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To observe if any property annotated with Publisher changed you can use didChange:
model.didChange.listen(() => doSomething())
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If you want to enableLogging you can override getter enableLogging:

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

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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();
}
}

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