如何将回调样本转换为延迟对象? [英] How to convert callback sample to deferred object?

问题描述

我有一个接受回调函数的函数，该函数将数据传回.可以将其转换为递延对象以进行更好的练习吗?

I have a function that accepts a callback function where I pass the data back in. Can this converted to a deferred object for better practice?

这就是我得到的:

    var chapters;
    var getChapters = function (fnLoad) {
        //CACHE DATA IF APPLICABLE
        if (!chapters) {
            //CALL JSON DATA VIA AJAX
            $.getJSON('/chapters.txt')
                .done(function (json) {
                    //STORE DATA IN LOCAL STORAGE
                    chapters = Lawnchair(function () {
                        this.save(json, function (data) {
                            //CALL CALLBACK ON DATA
                            fnLoad(data);
                        });
                    });
                });
        } else {
            //RETURN ALREADY CREATED LOCAL STORAGE
            chapters.all(function (data) {
                //CALL CALLBACK ON DATA
                fnLoad(data);
            });
        }
    };

然后我像这样简单地使用它:

Then I simply use it like this:

this.getChapters(function (data) {
    console.log(data);
});

在保持高速缓存方法的同时，如何像承诺一样使用它?

How can I use it like a promise though while maintaining the cache approach?

this.getChapters().done(function (data) {
    console.log(data);
});

推荐答案

var chapters;
var getChapters = function (fnLoad) {
    var d = new $.Deferred();
    //CACHE DATA IF APPLICABLE
    if (!chapters) {
        //CALL JSON DATA VIA AJAX
        $.getJSON('/chapters.txt')
            .done(function (json) {
                //STORE DATA IN LOCAL STORAGE
                chapters = Lawnchair(function () {
                    this.save(json, function (data) {
                        //CALL CALLBACK ON DATA
                        d.resolve(data);
                    });
                });
            })
            .fail(function() { d.reject(); });
    } else {
        //RETURN ALREADY CREATED LOCAL STORAGE
        chapters.all(function (data) {
            //CALL CALLBACK ON DATA
            d.resolve(data);
        });
    }
    return d.promise();
};

相关示例

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