试图用.then，.fail和.reject打破jQuery Promise链 [英] attempting to break jQuery promise chain with .then, .fail and .reject

问题描述

更新:此问题是jQuery 1.7 vs 1.8的结果.切勿在1.7中使用promise，因为它们不能与在.then中返回promise链接在一起. 1.8看起来他们并没有搞砸.

Update: this issue was a result of jQuery 1.7 vs 1.8. Do not ever use promises in 1.7 beacuse they aren't chainable with returning a promise inside a .then. 1.8 looks like they didn't mess it up.

http://jsfiddle.net/delvarworld/28TDM/

// make a promise
var deferred = $.Deferred();
promise = deferred.promise();

// return a promise, that after 1 second, is rejected
promise.then(function(){
    var t = $.Deferred();
    setTimeout(function() {
        console.log('rejecting...');
        t.reject();
    }, 1000);

    return t.promise();
});

// if that promise is successful, do this
promise.then(function() {
    console.log('i should never be called');
})

// if it errors, do this
promise.fail(function() {
    console.log('i should be called');
});

deferred.resolve();

预期:应该给我打电话"

Expected: 'i should be called'

实际:我永远都不会被呼唤"

Actual: 'i should never be called'

问题:我想链接回调，并使它们中的任何一个都能够断开链接并触发fail函数，并跳过其他链接的回调.我不明白为什么会触发所有事件，而不会触发失败.

Problem: I want to chain callbacks and have any one of them be able to break the chain and trigger the fail function, and skip the other chained callbacks. I don't understand why all of the thens are triggered and the fail is not triggered.

我来自NodeJS的Q库，因此我首先使用.then进行了尝试.但是，将其更改为.pipe无效.

I'm coming from NodeJS's Q library, so I tried it with .then first. However, changing it to .pipe has no effect.

推荐答案

您没有重新定义promise的值，请尝试以下操作:

You aren't re-defining the value of promise, try this:

http://jsfiddle.net/28TDM/1/

var deferred = $.Deferred();
promise = deferred.promise();

promise = promise.then(function(){
    var t = $.Deferred();
    setTimeout(function() {
        console.log('rejecting...');
        t.reject();
    }, 1000);

    return t.promise();
});

promise.then(function() {
    console.log('i should never be called');
})

promise.fail(function() {
    console.log('i should be called');
});

deferred.resolve();

显然，它以您认为的方式工作，它只是没有记录在案

Apparently it does work the way you thought it did, it just isn't documented https://api.jquery.com/deferred.then. Very cool. This is new functionality added in jQuery 1.8.0, more than likely they just aren't done updating the documentation.

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