SyncProviderTransformerMixin<InT, ValueT> mixin base

A mixin for custom ProviderListenables that do not emit AsyncValue.

If in error state, an exception will happen when trying to read the state of this listenable.

Usage

To use this mixin, you must implement the transform method, along with the source getter. The source will be the original provider that you are transforming. And transform is where your transformation logic will be defined.

The following example implements a variable of ProviderListenableSelect.select, where the callback returns a boolean instead of the selected value.

final class Where<T> with SyncProviderTransformerMixin<T, T> {
  Where(this.source, this.where);
  @override
  final ProviderListenable<T> source;
  final bool Function(T previous, T value) where;

  @override
  ProviderTransformer<T, T> transform(
    ProviderTransformerContext<T, T> context,
  ) {
     return ProviderTransformer(
       initState: (_) => context.sourceState.requireValue,
       listener: (self, previous, next) {
         if (where(previous, next))
           self.state = next;
       },
     );
  }
}

extension<T> on ProviderListenable<T> {
  ProviderListenable<T> where(
    bool Function(T previous, T value) where,
  ) => Where<T>(this, where);
}

Used as ref.watch(provider.where((previous, value) => value > 0)).

See also:

Implemented types
Available extensions
  1. @publicInMisc

Properties

hashCode → int
The hash code for this object.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
source → ProviderListenable<InT>
The source of this transformer.
no setterinherited

Methods

noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
select<OutT>(OutT selector(InT value)) → ProviderListenable<OutT>

Available on ProviderListenable<InT>, provided by the ProviderListenableSelect extension

Partially listen to a provider.
toString() → String
A string representation of this object.
inherited
transform(ProviderTransformerContext<InT, ValueT> context) → ProviderTransformer<InT, ValueT>
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited