javascript - Knockout JS 模型继承

Question

我的应用程序中有三个相对相似的淘汰模型，我想扩展一个基本模型以结合公共属性，而不是重复自己三次。

例子

var ItemModel = function (item) {
  var self = this;

  self.order = ko.observable(item.order);
  self.title = ko.observable(item.title);
  self.price = ko.observable(item.price);
  self.type = ko.observable(item.type);
};

var StandardItemModel = function (item, cartItemTypes) {
  var self = this;

  self.order = ko.observable(item.order);
  self.title = ko.observable(item.title);
  self.price = ko.observable(item.price);
  self.type = ko.observable(item.type);

  self.isInCart = ko.computed(function () {
    return cartItemTypes().indexOf(item.type) > -1;
  }, self);

  self.itemClass = ko.computed(function () {
     return self.isInCart() ? "icon-check" : "icon-check-empty";
  }, self);
};

var CustomItemModel = function (item) {
  var self = this;

  self.order = ko.observable(item.order);
  self.title = ko.observable(item.title);
  self.price = ko.observable(item.price);
  self.type = ko.observable(item.type);

  self.icon = item.icon;
};

我想使用 ItemModel 作为基类，并根据需要添加额外的属性。

Answer 1

我认为您可以像这样使用 ko.utils.extend

ko.utils.extend(self, new ItemModel(item));

在 StandardItemModel 内

像这样：http: //jsfiddle.net/marceloandrader/bhEQ6/

Answer 2

我想你可以这样做：

var StandardItemModel = function (item, cartItemTypes) {
var self = this;
self.standard = new ItemModel(item);
self.isInCart = ko.computed(function () {
return cartItemTypes().indexOf(item.type) > -1;
}, self);

self.itemClass = ko.computed(function () {
 return self.isInCart() ? "icon-check" : "icon-check-empty";
 }, self);
}

Answer 3

function MyBaseType() {
    var self = this;
    self.Id = 1
}

function MyComplexType() {
    var self = this;

    //Extending this class from MyBaseType
    ko.utils.extend(self, new MyBaseType());

    self.Name = 'Faisal';

    self.MyComplexSubType = new MyComplexSubType();
}

function MyComplexSubType() {
    var self = this;

    self.Age = 26;
}

JSFIDDLE 示例

Answer 4

您可以使用 .call 或 .apply 链接构造函数调用

function ItemModel (item) {
    var self = this;

    self.order = ko.observable(item.order);
    self.title = ko.observable(item.title);
    self.price = ko.observable(item.price);
    self.type = ko.observable(item.type);
}

function StandardItemModel(item, cartItemTypes) {
    var self = this;

    ItemModel.call(this, item);

    self.isInCart = ko.computed(function () {
        return cartItemTypes().indexOf(item.type) > -1;
    }, self);

    self.itemClass = ko.computed(function () {
        return self.isInCart() ? "icon-check" : "icon-check-empty";
    }, self);
}

function CustomItemModel (item) {
    var self = this;

    ItemModel.apply(this, [item]);

    self.icon = item.icon;
}

The advantage over ko.utils.extend (or similar methods from jQuery, underscore, etc) is that you are not creating an additional object just to grab references to its methods.

Answer 5

我做了类似的事情，经过大量的反复试验，但我得到了这个为我工作：

var StandardItemModel = function (item, cartItemTypes) {
    var self = this;
    ItemModel.call(self, item)
}

然后，您需要添加一个原型构造函数：

StandardModel.prototype = new ItemModel();

如果您想拥有通用方法，则需要使用原型将它们添加到基类中以添加它们，然后使用以下方法在更高的类中调用它们：

ItemModel.prototype.methodName.call(self, parameters);