Observer<State> class abstract

Observer Pattern - Observer

The Observer class is an abstract class that defines the behavior of an observer in the Observer Pattern. An observer is an object that watches a subject and receives updates when the subject's state changes.

The observer can be attached to or detached from a Subject.

When there's a change in the state of the subject, the observer is notified through a function called update. This function can then perform some actions with the new state information provided to it by the subject.

Alternative Constructors

It's provided alternative constructors to create an observer.

• coupled - Creates a CallbackCoupledObserver that is notified when is attached or detached from a subject
• stream - Creates a StreamObserver that can be listened to
• stateful - Creates a StatefulObserver that holds the last state of the subject

Implementers

• Callbackable
• CallbackObserver
• CoupledObserver
• ObserverState
• StatefulObserver

Constructors

Observer.new(ObserverCallback<State> callback)

factory

Observer.coupled({CoupledObserverCallback<State>? attached, CoupledObserverCallback<State>? detached})

factory

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

update(Subject<State> subject, State state) → void

This method is called whenever there is a change in the state of the Subject.

Operators

operator ==(Object other) → bool

The equality operator.

inherited

Static Methods

stateful<State>() → StatefulObserver<State>

stream<State>({bool sync = true, bool autoDispose = false}) → StreamObserver<State>