如何在JavaScript ES6类中链接异步方法 [英] How to chain async methods in javascript ES6 classes

问题描述

我想链接一个类的方法。我有同步方法的问题，但我不知道如何使用异步方法。

I want to chain methods from a class. I have o problems with synchronous methods, but I don't know how to do it with asynchronous methods.

例如，这个类：

class Example {

  constructor() {
    this.val = 0
  }

  async () {
    setTimeout(() => {
      this.val += 1
      return this
    }, 5000)
  }

  sync () {
    this.val += 1
    return this
  }

  check () {
    console.log('checker', this.val)
    return this
  }

}

这样做：

new Example().sync().check()
> 1

但这不起作用：

new Example().async().check()
> TypeError: Cannot read property 'check' of undefined

P.S。我想要链接，而不是地狱回调。

P.S. I want chaining, not Hell Callbacks.

推荐答案

我希望你想要调用 check（） / code>超时后过期。问题是，叉子不能立即有东西可以返回。

I expect that you want to call check() after the timeout has expired. The problem is that forks off, and you can't immediately have something available to return.

你可以传入 check（）作为回调：

class Example {

  constructor() {
    this.val = 0
  }

  async (callback) {
    setTimeout(() => {
      this.val += 1
      callback()
    }, 5000)
  }

  sync () {
    this.val += 1
    return this
  }

  check () {
    console.log('checker', this.val)
    return this
  }

}

// execution
var ex = new Example();
ex.async(ex.check)

...或承诺

class Example {

  constructor() {
    this.val = 0
  }

  async (callback) {
    var deferred = Q.defer()
    setTimeout(() => {
      this.val += 1
      deferred.resolve();
    }, 5000)
    return deferred.promise;
  }

  sync () {
    this.val += 1
    return this
  }

  check () {
    console.log('checker', this.val)
    return this
  }

}

// execution
var ex = new Example()
ex.async().then(() => ex.check())

...或者您可以使用ES6生成器

... Or you could use ES6 generators

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