使用 rxjs 来限制回调 [英] Using rxjs to throttle a callback

问题描述

我正在使用一个 API，我在其中注册了一个频繁发生的回调.

I am consuming an API in which I register a callback that occurs frequently.

function myCallback(event) {
  // do things with event, something computationally intensive
}

const something = createSomething({
  onSomethingHappened: myCallback
})

我想限制触发此回调的速率，可能使用 throttle.该项目使用捆绑了 rx 的 Angular.如何调整我的代码，以便 myCallback 使用 rx 将其限制在 300 毫秒?

I'd like to limit the rate at which this callback fires, probably using throttle. This project uses Angular which bundles rx. How can I adapt my code so myCallback it throttled at 300ms using rx?

我对 observables 的工作原理有一个基本的了解，但弄清楚回调接口如何转换为 observable 接口有点令人困惑.

I have a basic grasp on how observables work but it's been a bit confusing to figure out how the callback interface would convert to observable interface.

(随着答案的出现而编辑)

(edited as answers come)

推荐答案

我认为你可以使用 fromEventPattern:

let something;

const src$ = fromEventPattern(
  handler => (something = createSomething({ onSomethingHappened: handler })),
);

src$.pipe(
  throttleTime(300),
  map(args => myCallback(args))
);

注意:这里假设 myCallback 是一个同步操作.

Note: this assumed that myCallback is a synchronous operation.

传递给 fromEventPattern 的第一个参数是 addHandler.它还可以有 removeHandler，您可以在其中放置您的拆卸逻辑(例如:从内存中释放、清除值等).

The first argument passed to fromEventPattern is the addHandler. It can also have the removeHandler, where you can put your teardown logic(e.g: releasing from memory, nulling out values etc).

为了更好地理解什么是 handler 以及为什么在那里使用它，让我们看看 fromEventPattern 是如何实现的:

In order to get a better understanding of what is handler and why is it used there, let's see how fromEventPattern is implemented:

return new Observable<T | T[]>(subscriber => {
  const handler = (...e: T[]) => subscriber.next(e.length === 1 ? e[0] : e);

  let retValue: any;
  try {
    retValue = addHandler(handler);
  } catch (err) {
    subscriber.error(err);
    return undefined;
  }

  if (!isFunction(removeHandler)) {
    return undefined;
  }

  // This returned function will be called when the observable
  // is unsubscribed. That is, on manual unsubscription, on complete, or on error.
  return () => removeHandler(handler, retValue) ;
});

来源.

如你所见，通过 handler，你可以让返回的 observable 在需要发出一些东西的时候.

As you can see, through handler, you can let the returned observable when it's time to emit something.

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