有条件的承诺 [英] Conditional promises

问题描述

在我的剧本，我需要检索字典来转换EN codeD值成名字：

In my script, I need to retrieve a dictionary to convert encoded values into names:

$.ajax({
    // retrieve dictionary
})
.done(function(dictionary){
    // convert encoded values into names
})
.done(function(){
    // run my application
});

不过，有时字典已加载另一个应用程序，在这种情况下，我不需要Ajax调用：

However, sometimes the dictionary has already been loaded by another application, and in this case I don't need the ajax call:

if (dictionary) {
    // convert encoded values into names
    // run my application
}
else {
$.ajax({
    // retrieve dictionary
})
.done(function(dictionary){
    // convert encoded values into names
})
.done(function(){
    // run my application
});
}

这if / else语句是相当重的，有没有办法把它缩短：

This if/else statement is rather heavy, is there a way to make it shorter:

// load dictionary if needed
// then run my application

注：我用$符号为我的假code，但我不必拘泥于jQuery的

Note: I used the $ sign for my pseudo-code, but I am not necessarily tied to jQuery.

推荐答案

也许创建$。当一个假的承诺？

Maybe create a bogus promise with $.when?

var promise;
if (dictionary) promise = $.when(dictionary);
else {
    promise = $.ajax({

    })
    .done(function(dictionary){
        // convert encoded values into names
    });
}

promise
    .done(function(){
        // run my application
    });

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