inheritFrom<T extends InheritedModel<Object> > method
Null safety
- BuildContext context,
- {Object? aspect}
Makes context
dependent on the specified aspect
of an InheritedModel
of type T.
When the given aspect
of the model changes, the context
will be
rebuilt. The updateShouldNotifyDependent method must determine if a
change in the model widget corresponds to an aspect
value.
The dependencies created by this method target all InheritedModel ancestors of type T up to and including the first one for which isSupportedAspect returns true.
If aspect
is null this method is the same as
context.dependOnInheritedWidgetOfExactType<T>()
.
If no ancestor of type T exists, null is returned.
Implementation
static T? inheritFrom<T extends InheritedModel<Object>>(BuildContext context, { Object? aspect }) {
if (aspect == null) {
return context.dependOnInheritedWidgetOfExactType<T>();
}
// Create a dependency on all of the type T ancestor models up until
// a model is found for which isSupportedAspect(aspect) is true.
final List<InheritedElement> models = <InheritedElement>[];
_findModels<T>(context, aspect, models);
if (models.isEmpty) {
return null;
}
final InheritedElement lastModel = models.last;
for (final InheritedElement model in models) {
final T value = context.dependOnInheritedElement(model, aspect: aspect) as T;
if (model == lastModel) {
return value;
}
}
assert(false);
return null;
}