Allow StateNotifierProvider builder context to access the newly created StateNotifierProvider

[biklas7]

I'm providing a state notifier that will only be used on a specific page. It would be cool to do something like this change on Provider dev release.

https://pub.dev/packages/provider/versions/4.1.0-dev+3#-changelog-tab-

Added builder on the different providers. This parameters simplifies situations where we need a BuildContext that can access the new provider.

As such, instead of:

Provider(
  create: (_) => Something(),
  child: Builder(
    builder: (context) {
      final name = context.select((Something s) => s.name);
      return Text(name);
    },
  ),
)
we can write:

Provider(
  create: (_) => Something(),
  builder: (context, child) {
    final name = context.select((Something s) => s.name);
    return Text(name);
  },
)
The behavior is the same. This is only a small syntax sugar.

[smiLLe]

You might want to have a look at StateNotifierBuilder https://github.com/rrousselGit/state_notifier/tree/master/packages/flutter_state_notifier#statenotifierbuilder

[biklas7]

I don't think that's enough it says there:

but does not create/dispose/provide the object.

As opposed to StateNotifierProvider, this will not make read/update of StateNotifier work.

Which are features I want to support.

[rrousselGit]

The parameter is already there though

[biklas7]

So, the StateNotifierBuilder is the way to go here?

Only have to dispose the StateNotifier manually...

[rrousselGit]

No

I said that the builder parameter is already there

[biklas7]

Ah sorry didn't understand that.

If I use the builder parameter like specified on the issue description I get an error, the only way to make it work is using the child parameter with the builder widget.

That's why I've opened the issue. I though it wasn't working like on provider dev version.

Let me reproduce the error and post the log.

[biklas7]

Having something like this:

@override
  Widget build(BuildContext context) {
    return StateNotifierProvider<LoginStateNotifier, LoginState>(
      create: (_) => LoginStateNotifier(),
      builder: (context, child) {
        final loginState = context.watch<LoginState>();

        return Container();
      },
    );
  }

Causes the error:

════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following assertion was thrown building _InheritedProviderScope<LoginState>(dirty, controller: <not yet loaded>, value: <not yet loaded>):
A build function returned null.

The offending widget is: _InheritedProviderScope<LoginState>
Build functions must never return null.

To return an empty space that causes the building widget to fill available room, return "Container()". To return an empty space that takes as little room as possible, return "Container(width: 0.0, height: 0.0)".

The relevant error-causing widget was: 
  _InheritedProviderScope<LoginState> file:///home/antonio/Documents/flutter/.pub-cache/hosted/pub.dartlang.org/provider-4.1.0-dev+3/lib/src/inherited_provider.dart:126:12
When the exception was thrown, this was the stack: 
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 195:49  throw_
packages/flutter/src/widgets/debug.dart 276:7                                 <fn>
packages/flutter/src/widgets/debug.dart 296:12                                debugWidgetBuilderValue
packages/flutter/src/widgets/framework.dart 4507:7                            performRebuild
packages/provider/src/inherited_provider.dart 354:11                          performRebuild
...
════════════════════════════════════════════════════════════════════════════════════════════════════

But doing this:

@override
  Widget build(BuildContext context) {
    return StateNotifierProvider<LoginStateNotifier, LoginState>(
      create: (_) => LoginStateNotifier(),
      child: Builder(
        builder: (context) {
          final loginState = context.watch<LoginState>();

          return Container();
        },
      ),
    );
  }

Works!

[biklas7]

Am I doing something wrong here?

[rrousselGit]

Eh, I've just realised that the parameter is there but I forgot to implement it

I'll fix it in a moment

On Thu, 30 Apr 2020, 20:44 António Valente, notifications@github.com wrote:

Am I doing something wrong here?

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