createSelector2

Selector<S, R> createSelector2<S, T1, T2, R>(

  1. Selector<S, T1> selector1,

  2. Selector<S, T2> selector2,
  3. R combiner(
    1. T1,
    2. T2
    )
)

Creates a memoized selector with two input selectors.

Example:

final getVisibleTodos = createSelector2(
  getTodos,
  getFilter,
  (todos, filter) => switch (filter) {
    'completed' => todos.where((t) => t.completed).toList(),
    'active' => todos.where((t) => !t.completed).toList(),
    _ => todos,
  },
);

Implementation

Selector<S, R> createSelector2<S, T1, T2, R>(
  Selector<S, T1> selector1,
  Selector<S, T2> selector2,
  R Function(T1, T2) combiner,
) {
  T1? lastInput1;
  T2? lastInput2;
  R? lastResult;
  var hasCache = false;

return (S state) {
final input1 = selector1(state);
final input2 = selector2(state);


if (hasCache &&
identical(input1, lastInput1) &&
identical(input2, lastInput2)) {
return lastResult as R;
}


lastInput1 = input1;
lastInput2 = input2;
lastResult = combiner(input1, input2);
hasCache = true;


return lastResult as R;
};
}