SubEffect class
Useful for side-effects and optionally canceling them.
SubEffect calls its effect synchronously on every build
, unless
keys is specified. In which case the effect is called again only if
any value inside keys as changed.
The following example uses SubEffect to subscribes to a Stream and cancels the subscription when the widget is disposed. If the Stream changes, it will cancel the listening on the previous Stream and listen to the new one.
Stream stream;
Widget build(BuildContext context) {
return SubEffect(
effect: () {
final subscription = stream.listen(print);
// This will cancel the subscription when the widget is disposed
// or if the callback is called again.
return subscription.cancel;
},
// when the stream changes, useEffect will call the callback again.
keys: [stream],
child: /* ... */,
);
}
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- SubValue<
VoidCallback?> - SubEffect
Constructors
- SubEffect({required VoidCallback? effect(), required Widget child, SubValueKeys? keys})
- Useful for side-effects and optionally canceling them.
Properties
-
builder
→ SubValueBuild<
VoidCallback?> -
Creates the child of this Widget with the value.
finalinherited
-
create
→ SubValueBuilderCreate<
VoidCallback?> -
Creates the value. Called at least once and everytime keys changes.
finalinherited
-
dispose
→ SubValueBuilderDispose<
VoidCallback?> ? -
Disposes the value. Called before recreation and when disposing. Useful for Listeners, etc.
finalinherited
- hashCode → int
-
The hash code for this object.
no setterinherited
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- keys → SubValueBuilderKeys?
-
Used to decide when to recreate the value. If null, the value is never recreated.
finalinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
-
update
→ SubValueBuilderUpdate<
VoidCallback?> ? -
Updates the value. Called every build. If null, does nothing.
In the call order, this comes after recreating the value.
finalinherited
Methods
-
createElement(
) → StatefulElement -
Creates a StatefulElement to manage this widget's location in the tree.
inherited
-
createState(
) → State< SubValue< VoidCallback?> > -
Creates the mutable state for this widget at a given location in the tree.
inherited
-
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}) → 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