在Promise中更直接地使用函数 [英] Using a function more directly in a promise

问题描述

有没有一种表达方式:

    imagePFFileFromUrl(exampUrl) // (returns a promise)
    .then(function(xxx))
        // that syntax gives you the results of the
        // imagePFFileFromUrl inside the variable xxx.
        // I then use it in another function which
        // returns another promise...
        {
        return saveImageFile(xxx, anotherArgument) // (returns a promise)
        })
    .then(function(savedPFFile)

更像这样..

    imagePFFileFromUrl(exampUrl)
    .then(saveImageFile(...the results from imagePFFileFromUrl ...))
    .then(function(savedPFFile)

何时使用诺言?

推荐答案

您的.then()需要具有1或2个回调函数.如果为1，则采用承诺的已解决值.如果有两个，则第二个接受承诺的拒绝值.所以，不，您不能做您想做的事情.

Your .then()'s need to have 1 or 2 call back functions. If there is 1, it takes in the resolved value of the promise. If there are two, the second takes the rejected value of the promise. So, no, you can't do what you are trying to do.

这是该模式的很好的示例，带有两个参数，请注意return synchUsers

Here's a good example of the pattern, with two arguments, notice at return synchUsers

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