[英]Flutter riverpod debounce multiple dependent providers
如 Riverpod 文档中所述,Riverpod 提供者可以监视其他提供者来制作“处理管道”。
我有这样的事情:
final prov = Provider<String>((ref){
final w1 = ref.watch(prov1);
final w2 = ref.watch(prov2);
final w3 = ref.watch(prov3);
final w4 = ref.watch(prov4);
final complex = expensiveFunction(w1,w2,w3,w4);
return complex;
});
prov1
到prov4
可以通过 UI 的各个位单独修改,但是某些 UI 操作会导致它们中的部分或全部快速连续更改。
在w1
.. w4
都没有改变 2 秒之前,我怎样才能消除对expensiveFunction()
的调用?
从riverpod package的作者的 这条推文中,您可以这样做:
/// An extension on [Ref] with helpful methods to add a debounce.
extension RefDebounceExtension on Ref {
/// Delays an execution by a bit such that if a dependency changes multiple
/// time rapidly, the rest of the code is only run once.
Future<void> debounce(Duration duration) {
final completer = Completer<void>();
final timer = Timer(duration, () {
if (!completer.isCompleted) completer.complete();
});
onDispose(() {
timer.cancel();
if (!completer.isCompleted) {
completer.completeError(StateError('Cancelled'));
}
});
return completer.future;
}
}
final prov = FutureProvider<String>((ref) async {
final w1 = ref.watch(prov1);
final w2 = ref.watch(prov2);
final w3 = ref.watch(prov3);
final w4 = ref.watch(prov4);
await debounce(Duration(seconds: 2));
final complex = expensiveFunction(w1,w2,w3,w4);
return complex;
});
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