dart - Dart 和 Flutter 中具有强类型属性的匿名对象

Question

我在我的 Dart 中使用以下代码，它使用 redux 和 flutter_redux 包。一切正常，但如您所见，我必须使用以下语法来调用适当的操作。

callback['onIncrement'](34) 

它有效，但它很丑。我怎样才能改进它，让它看起来更像这样:

callback.onIncrement(34)

代码如下:

StoreConnector<AppState,Map<String,Function>>(
    converter: (store) {
      return {
        'onIncrement': (value) => store.dispatch(IncrementAction(value)), 
        'onDecrement': () => store.dispatch(Actions.decrement)
      };
    },
    builder: (context, callback) {
      return Column(
        children: <Widget>[
          FlatButton(
          child: Text('Increment Counter', style: TextStyle(color: Colors.white)),
          color: Colors.orange, 
          onPressed: () => callback['onIncrement'](1)

更新:

现在，我正在使用枚举，它稍微好一点:

StoreConnector<AppState,Map<Actions,Function>>(
        converter: (store) {
          return {
            Actions.increment: (value) => store.dispatch(IncrementAction(value)), 
            Actions.decrement: () => store.dispatch(Actions.decrement)
          };
        },
        builder: (context, callback) {
          return Column(
            children: <Widget>[
              FlatButton(
              child: Text('Increment Counter', style: TextStyle(color: Colors.white)),
              color: Colors.orange, 
              onPressed: () => callback[Actions.increment](23)

Answer 1

据我所知，在 Dart 中不可能这样做。您应该使用 ViewModel 代替:

StoreConnector<AppState, ViewModel>(
  converter: ViewModel.fromStore,
  builder: (context, viewModel) {
    return FlatButton( 
      onPressed: () => viewModel.onIncrement(1),
      ...
    );
  },
}

...

class ViewModel {
  final void Function(int) onIncrement;
  final void Function(int) onDecrement;

  ViewModel({@required this.onIncrement, @required this.onDecrement});

  factory ViewModel.fromStore(Store store) {
    return ViewModel(
      onIncrement: (value) => store.dispatch(IncrementAction(value)),
      onDecrement: (value) => store.dispatch(DecrementAction(value)),
    );
  }
}