ProxyProvider2<T, T2, R> class Null safety

A provider that builds a value based on other providers.

The exposed value is built through either create or update, then passed to InheritedProvider.

As opposed to create, update may be called more than once. It will be called once the first time the value is obtained, then once whenever ProxyProvider rebuilds or when one of the providers it depends on updates.

ProxyProvider comes in different variants such as ProxyProvider2. This is syntax sugar on the top of ProxyProvider0.

As such, ProxyProvider<A, Result> is equal to:

ProxyProvider0<Result>(
  update: (context, result) {
    final a = Provider.of<A>(context);
    return update(context, a, result);
  }
);

Whereas ProxyProvider2<A, B, Result> is equal to:

ProxyProvider0<Result>(
  update: (context, result) {
    final a = Provider.of<A>(context);
    final b = Provider.of<B>(context);
    return update(context, a, b, result);
  }
);

This last parameter of update is the last value returned by either create or update. It is null by default.

update must not be null.

See also:

Inheritance

Constructors

ProxyProvider2({Key? key, Create<R>? create, required ProxyProviderBuilder2<T, T2, R> update, UpdateShouldNotify<R>? updateShouldNotify, Dispose<R>? dispose, bool? lazy, TransitionBuilder? builder, Widget? child})
Initializes key for subclasses.

Properties

builder TransitionBuilder?
Syntax sugar for obtaining a BuildContext that can read the provider created. [...]
final, inherited
hashCode int
The hash code for this object. [...]
@nonVirtual, read-only, inherited
key Key?
Controls how one widget replaces another widget in the tree. [...]
final, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited

Methods

build(BuildContext context) Widget
Describes the part of the user interface represented by this widget. [...]
inherited
buildWithChild(BuildContext context, Widget? child) Widget
A build method that receives an extra child parameter. [...]
inherited
createElement() → _InheritedProviderElement<R>
Creates a StatelessElement to manage this widget's location in the tree. [...]
inherited
debugDescribeChildren() List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent 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}) 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. [...]
@nonVirtual, inherited