Computed<T> constructor

Computed<T>(List<Reactive> _sources, T _compute(List<Reactive>))

Constructs a new Computed instance.

_sources is a list of Reactive instances whose values are used to compute the new value. _compute is a function that takes the list of Reactive instances and computes the new value.

Implementation

Computed(this._sources, this._compute) {
  _value = _compute(_sources);
  _controller.add(Snapshot(_value, _value));

  StreamGroup.merge(_sources.map((source) => source.stream)).listen((_) {
    final newValue = _compute(_sources);
    if (newValue != _value) {
      _value = newValue;
      _controller.add(Snapshot(_value, newValue));
    }
  });
}