Flutter redux: StoreConnector vs StoreProvider

Question

I've been using flutter_redux for only very few days and I'm wondering what's the difference between:

class BtnCustom extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final store = StoreProvider.of<AppState>(context);

    return FlatButton(
      onPressed: store.dispatch(MyCustomAction),
      child: Text(store.state.MyCustomTxt),
    );
  }
}

and

class BtnCustom extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return StoreConnector<AppState, _ViewModel>(
      converter: (store) => _ViewModel(
          txt: store.state.MyCustomTxt,
          onPressed: store.dispatch(MyCustomAction)),
      builder: (BuildContext context, _ViewModel vm) {
        return FlatButton(
          onPressed: vm.onPressed,
          child: Text(vm.txt),
        );
      },
    );
  }
}

class _ViewModel {
  final String txt;
  final void Function() onPressed;

  _ViewModel({this.txt, this.onPressed});
}

?

The first one seems so handy to use. Are they any advantages or drawbacks of using one over another I should be aware of?

According to the documentation, the StoreConnector will rebuild the widget in it so:

• Is it ok to not use a StoreConnector when you don't need to rebuild a widget?
• Is it ok to have multiple widgets within a StoreConnector?

Answer 1

StoreConnector gives you more control over widget, especially when you don't want to rebuild it. StoreConnector:

• lets you detect whether the ViewModel has changed (whether widget should be rebuilt) if you use distinct: true and override hashCode and == in your ViewModel;

• lets you skip widget rebuild altogether by quickly checking some specific store.state:

   StoreConnector<AppState, MyViewModel>(
       distinct: true,
       ignoreChange: (state) {      
           return state.someVariable == theValueIDontCareAbout;
       },
       ...
   ),
  
   class MyViewModel{
       @override
       bool operator ==(other) {
            return (other is MyViewModel) && (this.someVmVariable == other.someVmVariable);
       }
  
       @override
       int get hashCode {
           int result = 17;
           result = 37 * result + someVmVariable.hashCode;
           return result;
       }
   }
  

And some more fine-grained controls. Take a look at the documentation of StoreConnector's constructor. If multiple widgets inside store sonnector share the same ViewModel it is natural to have them like that. However, if it's possible to prevent them from rebulding by separating their ViewModels you can use separate StoreConnectors.