jQuery Deferred 无法解决

Question

我有一个这样的服务助手设置：

var service = {

getSettings: function () {

    var that = this,
     deferred = $.Deferred();

    that.getThingOne().done(function (data) {

        that.getThingTwo(data.Element).done(function (data) {

            deferred.resolve(data);
        });
    });
    return deferred.promise();
},

getThingTwo: function (elm) {

    return $.getJSON('http://ajax-call-here');
},

getThingOne: function () {

    var deferred = $.Deferred();
    navigator.geolocation.getCurrentPosition(deferred.resolve, deferred.reject, {
        enableHighAccuracy: true
    });
    return deferred.promise();
}

};

当我调用它做这样的事情时，我永远不会到达下面。怎么回事？

service.getSettings().done(function(data) {

    // never reach here
});

Answer 1

首先 - 您可以大大简化您的代码。 Promises 链是对延续本身概念的抽象。

getSettings: function () {
    var that = this; // this line can be avoided as well
    return this.getThingOne().then(function (data) {
        // returning from a `.then` will cause the promise to resolve with that
        // return value
        return that.getThingTwo(data.Element); 
    });
}

其次，你的承诺不起作用。尝试保留上下文：

getThingOne: function () {

    var deferred = $.Deferred();
    navigator.geolocation.getCurrentPosition(
    function(v){ deferred.resolve(v); }, // preserve context
    function(e){ deferred.reject(e;) }, { // here too
        enableHighAccuracy: true
    });
    return deferred.promise();
}

因此 - 承诺从未得到解决。