Notifier<State> class abstract

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.

When using autoDispose or family, your notifier type changes. Instead of extending Notifier, you should extend either:

Constructors

Notifier()

Properties

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

Methods

build() → State
Initialize a Notifier.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
toString() → String
A string representation of this object.
inherited
updateShouldNotify(State previous, State 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