javascript - backbone.js:覆盖到 JSON

Question

我正在尝试在 Backbone.Model 中实现某种嵌套集合

为此，我必须覆盖解析服务器响应并将数组包装到集合中的适配器函数，以及在没有任何辅助方法的情况下序列化整个对象的函数。我在使用第二个时遇到了问题。

var Model = Backbone.Model.extend({

    urlRoot: "/model",

    idAttribute: "_id",

    // this wraps the arrays in the server response into a backbone  collection
    parse: function(resp, xhr) {
        $.each(resp, function(key, value) {
            if (_.isArray(value)) {
                resp[key] = new Backbone.Collection(value);
            } 
        });
        return resp;
    },

    // serializes the data without any helper methods
    toJSON: function() {
        // clone all attributes
        var attributes = _.clone(this.attributes);

        // go through each attribute
        $.each(attributes, function(key, value) {
            // check if we have some nested object with a toJSON method
            if (_.has(value, 'toJSON')) {
                // execute toJSON and overwrite the value in attributes
                attributes[key] = value.toJSON();
            } 
        });

        return attributes;
    }

});

现在问题出在 toJSON 的第二部分。出于某种原因

_.has(value, 'toJSON') !== true

不返回真

谁能告诉我哪里出了问题？

Answer 1

Underscore's has这样做:

has _.has(object, key)

Does the object contain the given key? Identical to object.hasOwnProperty(key), but uses a safe reference to the hasOwnProperty function, in case it's been overridden accidentally.

但是您的 value 不会有 toJSON 属性，因为 toJSON 来自原型(prototype)(参见 http://jsfiddle.net/ambiguous/x6577/ )。

您应该改用 _(value.toJSON).isFunction():

if(_(value.toJSON).isFunction()) {
    // execute toJSON and overwrite the value in attributes
    attributes[key] = value.toJSON();
}