RebuildRule<T> constructor

RebuildRule<T>({ required T value(), required Object? observedState(), Object? beside()?, })

A rule over value and observedState: the controller's value, and everything a reader can see of the controller as one value with value equality.

For most controllers both are the value. An infinite query's controller also keeps its paging flags beside the result — a fetch that switches direction leaves the result untouched — so its observed state is InfiniteQueryController.observedState, the result and the flags together.

beside is the part of observedState that is not in value, when there is one: for an infinite query, the paging flags alone. A reader shows it, but buildWhen compares values and never sees it, so when it moves the reader rebuilds whatever buildWhen says of the value. Leave it out where the observed state is the value, or the value under an equality of its own.

final rule = RebuildRule<QueryResult<Post>>(
  value: () => feed.value,
  observedState: () => (feed.value, feed.hasNextPage),
  beside: () => feed.hasNextPage,
);

Implementation

RebuildRule({
  required T Function() value,
  required Object? Function() observedState,
  Object? Function()? beside,
})  : _value = value,
      _observedState = observedState,
      _beside = beside;