Take方法有什么用？ Flutter & dart

Question

take --> 起什么作用（flutter和Dart）

class Ticker {
  Stream<int> tick({int ticks}) => Stream.periodic(Duration(seconds: 1), (x) {
        return ticks - x - 1;
      }).take(ticks);
}

Answer 1

很簡單，它只需要從 stream 傳遞的項目數（ticks 參數）。

// This stream is responsible to do a task for each second 
Stream.periodic(Duration(seconds: 1), (x) {
    return ticks - x - 1;
})

// With take, stream does it's job only `ticks` times
Stream.periodic(Duration(seconds: 1), (x) {
    return ticks - x - 1;
}).take(ticks);