Notifier<ValueT> class abstract Notifiers

A class which exposes a state that can change over time.

For example, Notifier can be used to implement a counter by doing:

final counterProvider = NotifierProvider<Counter, int>(Counter.new);

class Counter extends Notifier<int> {
  @override
  int build() {
    // Inside "build", we return the initial state of the counter.
    return 0;
  }

  void increment() {
    state++;
  }
}

We can then listen to the counter inside widgets by doing:

Consumer(
  builder: (context, ref) {
    return Text('count: ${ref.watch(counterProvider)}');
  },
)

And finally, we can update the counter by doing:

Consumer(
  builder: (context, ref) {
    return ElevatedButton(
      onTap: () => ref.read(counterProvider.notifier).increment(),
      child: const Text('increment'),
    );
  },
)

The state of Notifier is expected to be initialized synchronously. For asynchronous initializations, see AsyncNotifier.

Inheritance
Available extensions

Constructors

Notifier.new()

Properties

hashCode → int
The hash code for this object.
no setterinherited
ref → Ref
The Ref associated with this notifier.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
state ↔ ValueT
The value currently exposed by this notifier.
getter/setter pairinherited
stateOrNull → ValueT?
The value currently exposed by this Notifier.
no setterinherited

Methods

build() → ValueT
Initialize a Notifier.
listenSelf(void listener(ValueT? previous, ValueT next), {void onError(Object error, StackTrace stackTrace)?}) → RemoveListener
Listens to changes on the value exposed by this provider.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
persist<KeyT, EncodedT>(FutureOr<Storage<KeyT, EncodedT>> storage, {required KeyT key, required EncodedT encode(ValueT state), required ValueT decode(EncodedT encoded), StorageOptions options = const StorageOptions()}) → PersistResult

Available on AnyNotifier<StateT, ValueT>, provided by the NotifierPersistX extension

Persist the state of a provider to a database.
runBuild() → void
Executes Notifier.build.
override
toString() → String
A string representation of this object.
inherited
updateShouldNotify(ValueT previous, ValueT next) → bool
A method invoked when the state exposed by this Notifier changes. It compares the previous and new value, and return whether listeners should be notified.
inherited

Operators

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