createStructuredSelector

Selector<S, R> createStructuredSelector<S, R>(

  1. R compute(
    1. S state

    )
)

Structured selector that computes multiple derived values at once.

This is useful when you need to compute multiple derived values from the same base selectors.

Example:

final todoStats = createStructuredSelector<AppState, TodoStats>(
  (state) => (
    total: state.todos.length,
    completed: state.todos.where((t) => t.completed).length,
    active: state.todos.where((t) => !t.completed).length,
  ),
);

Implementation

Selector<S, R> createStructuredSelector<S, R>(R Function(S state) compute) {
  R? lastResult;
  S? lastState;
  var hasCache = false;

return (S state) {
if (hasCache && identical(state, lastState)) {
return lastResult as R;
}


lastState = state;
lastResult = compute(state);
hasCache = true;


return lastResult as R;
};
}