承诺的承诺到简单的承诺? [英] Promise of promise to simple promise?

问题描述

我一直在玩 Promise，通常可以弄清楚如何处理它们，但在这种情况下，我无法弄清楚如何删除一个 Promise 包装级别.

I've been playing with promises, and usually can figure out how to handle them well, but in this situation, I can't figure out how to remove one promise-wrapping level.

代码如下:

let promise2 = promise1.then((nodes) => {
  return Promise.all(nodes.map(n => {

    // findConnections returns a promise
    return this.findConnections(n.get("spotifyData")); 
  }));
});

现在我希望 promise2 包装一个数组，但它没有，它包装了一个包装数组的承诺.如果我想访问数组，我必须这样做:

Now I would expect promise2 to wrap an array, but it doesn't, it wraps a promise wrapping an array. If I want to access the array, I have to do this:

promise2.then(level1 => level1.then(level2 => console.log(level2)));

level1 本身就是一个承诺.

level1 is a promise itself.

当然，我可以使用它，但我发现代码非常难看，我想简化它以便您可以:

Of course, I could work with that, but I find the code very ugly, and I'd like to simplify it so that you can do:

promise2.then(level1 => console.log(level1))

然后直接在那里得到一个数组.

and directly get an array there.

有什么想法吗?

谢谢！

findConnections() 方法:

The findConnections() method:

findConnections: function (node) {
  return Ember.$.get("https://api.spotify.com/v1/artists/" + node.id + "/related-artists").then((data) => {
     return data.artists;
  });
}

推荐答案

level1 本身就是一个承诺.

不，不是.Ember 确实使用了 RSVP，即 Promises/A+ 兼容，这意味着 then 回调永远不会用承诺(或 thenable)调用.他们总是收到一个普通的值.

No it's not. Ember does use RSVP, which is Promises/A+ compatible, and that means that then callbacks are never called with a promise (or thenable). They always receive a plain value.

Promises/A+ 确实要求 then 没有返回嵌套的 Promise.它们总是递归解包.你可以这样做

Promises/A+ does mandate that there are no nested promises returned from then. They are always recursively unwrapped. You can just do

promise2.then(connections => console.log(connections));

如果这真的不起作用，则表明 promise1 不是真正的(或至少不符合标准的)承诺，您应该执行 promise1 = Promise.resolve(promise1) 首先.

If this really doesn't work, that would suggest that promise1 is no real (or at least no standard-conformant) promise, and you should do promise1 = Promise.resolve(promise1) first.

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