LocalPottery class
A widget that associates existing pots with new values and makes them accessible from descendants in the tree via the pots.
This widget defines new factories for existing pots and binds the objects created by them to the pots so that those objects are made available to descendants.
An important fact is that the factories of the existing pots are
not actually replaced, therefore calling the Pot.call method
still returns the object held in the global pot. Use NearestPotOf.of
instead to obtain the local object from the nearest LocalPottery
ancestor. The example below illustrates the behaviour.
final fooPot = Pot(() => Foo(111));
...
class ParentWidget extends StatelessWidget {
@override
Widget build(BuildContext context) {
return LocalPottery(
pots: {
fooPot: () => Foo(222),
},
builder: (context) {
print(fooPot()); // 111
print(fooPot.of(context)); // 222
return ChildWidget();
},
);
}
}
class ChildWidget extends StatelessWidget {
@override
Widget build(BuildContext context) {
print(fooPot()); // 111
print(fooPot.of(context)); // 222
...
}
}
This is useful when you need in descendants some objects that are different from the ones held in global pots but of the same type.
In the following example, a LocalPottery
provides its descendant
(TodoListPage) with a notifier for a specific category. It allows
the previous page to control which category the next page is
associated with.
Navigator.of(context).push(
TodoListPage.route(category: Category.housework),
);
...
class TodoListPage extends StatelessWidget {
const TodoListPage._();
static Route<void> route({required Category category}) {
return MaterialPageRoute(
builder: (context) => LocalPottery(
pots: {
todosNotifierPot: () => TodosNotifierPot(category: category),
},
builder: (context) => const TodoListPage(),
),
);
}
@override
Widget build(BuildContext context) {
// This is a notifier for a list of a specific category.
final notifier = todosNotifierPot.of(context);
return ValueListenableBuilder(
valueListenable: notifier,
builder: (context, state, child) {
return Scaffold(
appBar: AppBar(
// The title is "Housework" if the current
// notifier is for the category of housework.
title: Text(state.category.label),
),
...
);
},
);
}
}
Note that there are several important differences between
LocalPottery
and Pottery:
LocalPottery
creates an object immediately, whereasPottery
creates (replaces, more precisely) an object only if the relevant Pot already have one.- As already mentioned, objects created by
LocalPottery
are only accessible with NearestPotOf.of. - Objects created by
LocalPottery
are not automatically discarded when theLocalPottery
is removed from the tree. Use disposer to do clean-up.
Also note that an error arises only at runtime if the map contains wrong pairs of pot and factory. Make sure to specify a correct factory creating an object of the correct type.
It is advised that LocalPottery
be used only where it is
absolutely necessary. Using it too much may make it harder to
follow the code of your app.
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- LocalPottery
Constructors
- LocalPottery({Key? key, required PotOverrides pots, required WidgetBuilder builder, void disposer(LocalPotteryObjects)?})
-
Creates a LocalPottery widget that associates existing pots
with new values and makes them accessible from descendants in
the tree via the pots.
const
Properties
- builder → WidgetBuilder
-
A function called to obtain the child widget.
final
- disposer → (void Function(LocalPotteryObjects)?)
-
A function called when this LocalPottery is removed from
the tree permanently.
final
- hashCode → int
-
The hash code for this object.
no setterinherited
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- pots → PotOverrides
-
A map of pots and factories.
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< LocalPottery> -
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}) → 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