在 Coffeescript 中链接 Promise [英] Chaining Promises in Coffeescript

问题描述

有没有办法在 Coffeescript 中将 Promises 链接在一起.例如，考虑以下 javascript 代码，

Is there a way to chain Promises together in Coffeescript. For example, consider the following javascript code,

return $.getJSON('/api/post.json')
  .then(function(response) {
    // do something
  })
  .then(function(response) {
    // do something
  })
  .then(null, function(err) {
    // do something
  });

每个then的都是可选的，最后的then需要函数返回.目前我在coffeescript中写这个，

Each of the then's is optional, and the final then needs to be returned by the function. Currently I am writing this in coffeescript as,

promise = $.getJSON('/api/post.json')
promise = promise.then (response) ->
  // do something

promise = promise.then (response) ->
  // do something

promise = promise.then null, (err) ->
  // do something

return promise

有没有更好的方法来做到这一点?谢谢.

Is there a better way to do this? Thanks.

推荐答案

Ezekiel 显示了正确的方法，但它不需要在函数周围加上括号.做吧:

Ezekiel shows the right way, but it doesn't need the parentheses around the functions. Just do:

$.getJSON '/api/post.json' # As of CoffeeScript 1.7, you don't need the parentheses here either.
.then (response) ->
  # do something
  response # if you would not return anything, promise would be fulfilled with undefined
.then (response) ->
  # do something
  undefined # necessary to prevent empty function body
.then null, (err) ->
  # handle error

我认为它非常干净.比较麻烦的一件事是当您需要同时添加 onRejected 和 onFulfilled 处理程序时.

I think it's surprisingly clean. The one thing that's relatively messy is when you need to add onRejected and onFulfilled handlers at the same time.

注意:上次我检查时，这在 CoffeeScript Redux 中不起作用，但这是几个月前的事了.

Note: Last time I checked, this did not work in CoffeeScript Redux, but this was a few months ago.

注意 2:您需要在每个函数体中至少有一行实际代码(即不仅仅是注释)才能使其工作.通常情况下，你会，所以这不是一个大问题.

Note 2: You need at least one line of actual code (i.e. not just a comment) in each function body for this to work. Typically, you will, so it's not a big issue.

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