嵌套Backbone.js集合的更好解决方案

时间:2012-05-02 07:26:09

标签: backbone.js nested-attributes

我的许多Backbone模型经常处理嵌套模型和集合,到目前为止,我手动使用defaultsparsetoJSON的组合来实现嵌套:

ACME.Supplier = Backbone.Model.extend({
    defaults: function() {
        return {
            contacts: new ACME.Contacts(),
            tags: new ACME.Tags(),
            attachments: new ACME.Attachments()
        };
    },

    parse: function(res) {
        if (res.contacts) res.contacts = new ACME.Contacts(res.contacts);
        if (res.tags) res.tags = new ACME.Tags(res.tags);
        if (res.attachments) res.attachments = new ACME.Attachments(res.attachments);

        return res;
    }
});

ACME.Tag = Backbone.Model.extend({
    toJSON: function() {
        return _.pick(this.attributes, 'id', 'name', 'type');
    }
});

我看了几个插件,基本上和上面一样,但是控制和更多的样板很少,所以我想知道是否有人对这个常见的Backbone.js问题有更优雅的解决方案。


编辑:我最终采用了以下方法:

ACME.Supplier = Backbone.Model.extend({
    initialize: function(options) {
        this.tags = new ACME.Tags(options.tags);
    },

    parse: function(res) {
        res.tags && this.tags.reset(res.tags);

        return res;
    }
});

ACME.Tag = Backbone.Model.extend({
    toJSON: function() {
        return _.pick(this.attributes, 'id', 'name', 'type');
    }
});

值得注意的是,后来我发现你需要通过options对象将嵌套的模型/集合数据从构造函数传递到嵌套模型的构造函数中。

4 个答案:

答案 0 :(得分:8)

我认为你的做法没有任何问题。

恕我直言Model.parse()方法如果为此:在特殊解析行为需要时被覆盖

我唯一想改变的就是这样的事情:

if (res.tags) res.tags = new ACME.Tags(res.tags);

为此:

if (res.tags) this.tags.reset(res.tags);

由于您已经有ACME.Tags集合的实例,我会重复使用它。

我也不喜欢defaults实现,我习惯在Model.initialize()中进行初始化,但我认为这是一个品味问题。

答案 1 :(得分:3)

我发现通过这种方法,供应商的toJSON功能将会过时,因此从它的重新组装回JSON状态可能是一个好主意,这是儿童的数据。

ACME.Supplier = Backbone.Model.extend({
    initialize: function(options) {
        this.tags = new ACME.Tags(options.tags);
    },

    parse: function(res) {
        res.tags && this.tags.reset(res.tags);

        return res;
    },

    toJSON: function({
        return _.extend(
            _.pick(this.attributes, 'id', 'attr1', 'attr2'), {
            tags: this.tags.toJSON(),
        });
    })

});

答案 2 :(得分:2)

我们不想添加另一个框架来实现这一点,因此我们在基础模型类中将其抽象出来。 以下是您声明和使用它的方式(available as a gist):

// Declaration

window.app.viewer.Model.GallerySection = window.app.Model.BaseModel.extend({
  nestedTypes: {
    background: window.app.viewer.Model.Image,
    images: window.app.viewer.Collection.MediaCollection
  }
});

// Usage

var gallery = new window.app.viewer.Model.GallerySection({
    background: { url: 'http://example.com/example.jpg' },
    images: [
        { url: 'http://example.com/1.jpg' },
        { url: 'http://example.com/2.jpg' },
        { url: 'http://example.com/3.jpg' }
    ],
    title: 'Wow'
}); // (fetch will work equally well)

console.log(gallery.get('background')); // window.app.viewer.Model.Image
console.log(gallery.get('images')); // window.app.viewer.Collection.MediaCollection
console.log(gallery.get('title')); // plain string

它与settoJSON同样有效 这里是BaseModel

window.app.Model.BaseModel = Backbone.Model.extend({
  constructor: function () {
    if (this.nestedTypes) {
      this.checkNestedTypes();
    }

    Backbone.Model.apply(this, arguments);
  },

  set: function (key, val, options) {
    var attrs;

    /* jshint -W116 */
    /* jshint -W030 */
    // Code below taken from Backbone 1.0 to allow different parameter styles
    if (key == null) return this;
    if (typeof key === 'object') {
      attrs = key;
      options = val;
    } else {
      (attrs = {})[key] = val;
    }
    options || (options = {});
    // Code above taken from Backbone 1.0 to allow different parameter styles
    /* jshint +W116 */
    /* jshint +W030 */

    // What we're trying to do here is to instantiate Backbone models and collections
    // with types defined in this.nestedTypes, and use them instead of plain objects in attrs.

    if (this.nestedTypes) {
      attrs = this.mapAttributes(attrs, this.deserializeAttribute);
    }

    return Backbone.Model.prototype.set.call(this, attrs, options);
  },

  toJSON: function () {
    var json = Backbone.Model.prototype.toJSON.apply(this, arguments);

    if (this.nestedTypes) {
      json = this.mapAttributes(json, this.serializeAttribute);
    }

    return json;
  },

  mapAttributes: function (attrs, transform) {
    transform = _.bind(transform, this);
    var result = {};

    _.each(attrs, function (val, key) {
      result[key] = transform(val, key);
    }, this);

    return result;
  },

  serializeAttribute: function (val, key) {
    var NestedType = this.nestedTypes[key];
    if (!NestedType) {
      return val;
    }

    if (_.isNull(val) || _.isUndefined(val)) {
      return val;
    }

    return val.toJSON();
  },

  deserializeAttribute: function (val, key) {
    var NestedType = this.nestedTypes[key];
    if (!NestedType) {
      return val;
    }

    var isCollection = this.isTypeASubtypeOf(NestedType, Backbone.Collection),
        child;

    if (val instanceof Backbone.Model || val instanceof Backbone.Collection) {
      child = val;
    } else if (!isCollection && (_.isNull(val) || _.isUndefined(val))) {
      child = null;
    } else {
      child = new NestedType(val);
    }

    var prevChild = this.get(key);

    // Return existing model if it is equal to child's attributes

    if (!isCollection && child && prevChild && _.isEqual(prevChild.attributes, child.attributes)) {
      return prevChild;
    }

    return child;
  },

  isTypeASubtypeOf: function (DerivedType, BaseType) {
    // Go up the tree, using Backbone's __super__.
    // This is not exactly encouraged by the docs, but I found no other way.

    if (_.isUndefined(DerivedType['__super__'])) {
      return false;
    }

    var ParentType = DerivedType['__super__'].constructor;
    if (ParentType === BaseType) {
      return true;
    }

    return this.isTypeASubtypeOf(ParentType, BaseType);
  },

  checkNestedTypes: function () {
    _.each(this.nestedTypes, function (val, key) {
      if (!_.isFunction(val)) {
        console.log('Not a function:', val);
        throw new Error('Invalid nestedTypes declaration for key ' + key + ': expected a function');
      }
    });
  },
}

答案 3 :(得分:0)

面对同样的问题,我做了类似的事情(下面的代码是TypeScript编译器的输出,所以它有点冗长):

  var Model = (function (_super) {
    __extends(Model, _super);
    function Model() {
        _super.apply(this, arguments);
    }
    Model.prototype.fieldToType = function () {
        return {};
    };

    Model.prototype.parse = function (response, options) {
        _.each(this.fieldToType(), function (type, field) {
            if (response[field]) {
                if (_.isArray(response[field])) {
                    response[field] = _.map(response[field], function (value) {
                        return new type(value, { parse: true });
                    });
                } else {
                    response[field] = new type(response[field], { parse: true });
                }
            }
        });
        return _super.prototype.parse.call(this, response, options);
    };
    Model.prototype.toJSON = function () {
        var j = _super.prototype.toJSON.call(this);
        _.each(this.fieldToType(), function (type, field) {
            if (j[field]) {
                if (_.isArray(j[field])) {
                    j[field] = _.map(j[field], function (value) {
                        return value.toJSON();
                    });
                } else {
                    j[field] = j[field].toJSON();
                }
            }
        });
        return j;
    };
    return Model;
})(Backbone.Model);

然后我可以简单地覆盖fieldToType方法来定义我的字段类型:

PendingAssignmentOffer.prototype.fieldToType = function () {
    return {
        'creator': User,
        'task_templates': TaskTemplateModel,
        'users': User,
        'school_classes': SchoolClass
    };
};