CellWidget class abstract

A widget which is rebuilt in response to changes in the values of ValueCell's.

When the value of a ValueCell is referenced within the build method, using ValueCell.call, the widget is automatically rebuilt whenever the value of the referenced cell changes.

Example:

class Example extends WidgetCell {
  final ValueCell<int> a;

  Example({
    super.key
    required this.a
  });

  @override
  Widget build(BuildContext context) {
    return Text('The value of cell a is ${a()}');
  }
}

In the above example, the widget is rebuilt automatically whenever the value of cell a is changed.

Cells defined directly within the build will have their state persisted between builds. For this to happen the following rules have to be observed:

  1. Cells should not be defined in conditionals or loops.
  2. Cells should not be defined in callback or builder functions of widgets nested in this widget.

The following is an example of correctly placed cell definitions:

@override
Widget build (BuildContext context) {
  final count = MutableCell(0);
  final next = ValueCell.computed(() => count() + 1);
  ...
}

The following is an example of incorrectly placed cell definitions:

@override
Widget build (BuildContext context) {
  if (...) {
    // This is bad because the definition appears within a conditional
    final count = MutableCell(0);
  }

  while (...) {
    // This is bad because the definition appears within a loop
    final count = MutableCell(0);
  }

  return Builder((context) {
    // This is bad because the definition appears in a builder function
    // of a nested widget and the [CellWidget] will not be able to persist
    // its state between builds.
    final count = MutableCell(0);
  });
}
Inheritance
Implementers

Constructors

CellWidget({Key? key, String? restorationId})
const
CellWidget.builder(Widget builder(CellHookContext context), {Key? key, String? restorationId})
Create a CellWidget with the build method defined by builder.
factory

Properties

hashCode → int
The hash code for this object.
no setterinherited
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
restorationId → String?
Restoration ID to use for restoring the cell state
final
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

build(BuildContext context) → Widget
Describes the part of the user interface represented by this widget.
inherited
createElement() → StatelessElement
Creates a StatelessElement to manage this widget's 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