SubDefault<T> class
Creates a default value if the value passed in is null.
The create function is only ever called if null is passed for value. The dispose function is only called with values which have been created with the create function.
If a default value is created and a non-null value is passed later, the default value will be disposed.
The following example shows basic usage.
Widget build(BuildContext context) {
return SubDefault(
// Our value, which may be null.
value: maybeNullValue,
create: () => someDefaultValue,
// Will only dispose the default value.
dispose: (value) => value.dispose(),
// Will always receive a value.
builder: (context, value) => /* ... */,
);
}
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- SubValue<
_MaybeDefaultValue< T> > - SubDefault
Constructors
-
SubDefault({required T? value, required SubValueCreate<
T> create, SubValueKeys? keys, SubValueDispose<T> ? dispose, required SubValueBuild<T> builder}) - Creates a default value if the value passed in is null.
Properties
-
builder
→ SubValueBuild<
_MaybeDefaultValue< T> > -
Creates the child of this Widget with the value.
finalinherited
-
create
→ SubValueBuilderCreate<
_MaybeDefaultValue< T> > -
Creates the value. Called at least once and everytime keys changes.
finalinherited
-
dispose
→ SubValueBuilderDispose<
_MaybeDefaultValue< ?T> > -
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<
_MaybeDefaultValue< ?T> > -
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< _MaybeDefaultValue< >T> > -
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