Observer<T> class

A widget that rebuilds whenever the given observable emits a new value.

Similar to ValueListenableBuilder, but built around custom IObservable. Useful for simple UI bindings with minimal boilerplate.

Example usage: Observer(counter, (count) => Text('Count: $count')); or: Observer.builder( observable: counter, builder: (context, value) => Text('Count: $value'), );

Inheritance

Constructors

Observer(IObservable<T> observable, Widget builder(T v), {Key? key}): Shorthand constructor for when you don't need BuildContext in your builder.
factory
Observer.builder({Key? key, required IObservable<T> observable, required Widget builder(BuildContext ctx, T val)}): Builder constructor with access to both BuildContext and value.
factory

Properties

builder → Widget Function(BuildContext, T): The builder function that builds the UI based on the observable value.
final
hashCode → int: The hash code for this object.
no setterinherited
key → Key?: Controls how one widget replaces another widget in the tree.
finalinherited
observable → IObservable<T>: The observable to listen to.
final
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited

Methods

createElement() → StatefulElement: Creates a StatefulElement to manage this widget's location in the tree.
inherited
createState() → State<Observer<T>>: Creates the mutable state for this widget at a given location in the tree.
override
debugDescribeChildren() → List<DiagnosticsNode>: Returns a list of DiagnosticsNode objects describing this node's children.
inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void: Add additional properties associated with the node.
inherited
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) → DiagnosticsNode: Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.
inherited
toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) → String: A string representation of this object.
inherited
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug, int wrapWidth = 65}) → String: Returns a string representation of this node and its descendants.
inherited
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String: Returns a one-line detailed description of the object.
inherited
toStringShort() → String: A short, textual description of this widget.
inherited

Operators

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

Static Methods

multi({Key? key, required List<IObservable> observables, required Widget builder(BuildContext)}) → MultiObserver: Creates a MultiObserver that listens to a list of observables, and rebuilds the widget whenever any of them changes.
select<T, R>({Key? key, required IObservable<T> observable, required R selector(T), required Widget builder(BuildContext, R)}) → ObserverSelect<T, R>: Creates an ObserverSelect that listens to changes from an observable, and only rebuilds the widget when the selected value (from selector) changes.
three<A, B, C>({Key? key, required IObservable<A> o1, required IObservable<B> o2, required IObservable<C> o3, required Widget builder(BuildContext, A, B, C)}) → Observer3<A, B, C>: Creates an Observer3 that listens to three observables o1, o2, and o3, and rebuilds the widget whenever any of the values change.
two<A, B>({Key? key, required IObservable<A> o1, required IObservable<B> o2, required Widget builder(BuildContext, A, B)}) → Observer2<A, B>: Creates an Observer2 that listens to two observables o1 and o2, and rebuilds the widget whenever either value changes.