Javascript中的多级继承

Question

我试图使用原型在Javascript中模拟继承.

我有一个名为Model的函数和一个model => Item的类型.

var Model = function() { 
   this.names = ["name1", "name2"]; 
} 
Model.prototype.Item = function(args) { 
   this.init = function(item_name) { 
      this.names[0] = item_name; // ERROR: Cannot set property '0' of undefined
   } 
}
var m = new Model();
var i = new m.Item();
i.init("New Name"); // ERROR: Cannot set property '0' of undefined

如何names从init()上面的函数访问数组？

Answer 1

Javascript中的继承很棘手!阅读这篇文章,了解Javascript中传统面向对象继承的一个很好的解释:http://blog.slaks.net/2013-09-03/traditional-inheritance-in-javascript/.

var Model = function () {
    this.names = ["name1", "name2"];
};

var Item = function () {
    //When inheriting in Javascript you must 
    //call the inherited function's constructor manually.
    Model.call(this);
};

//Inherit Model's prototype so you get all of Model's methods.
Item.prototype = Object.create(Model.prototype);
Item.prototype.constructor = Item;

Item.prototype.init = function (item_name) {
    this.names[0] = item_name;
};

var Employee = function () {
    Model.call(this);
};

Employee.prototype = Object.create(Model.prototype);
Employee.prototype.constructor = Employee;

var myItem = new Item();
myItem.init("New Name");
//prints New Name, name2
console.log(myItem.names);


var myEmployee = new Employee();
//prints name1, name2
console.log(myEmployee.names);

更传统的面向对象语言(C#)中的类似代码:

public class Model
{
    public Model()
    {
        this.Names = new[] {"name1", "name2"};
    }
    public string[] Names { get; set; }
}

public class Item : Model
{
    public Item() : base() { }

    public void init(string item_name)
    {
        this.Names[0] = item_name;
    }
}

public class Employee : Model
{
    public Employee() : base() { }
}

var myItem = new Item();
myItem.init("New Name");
//prints New Name, name2
Console.WriteLine(String.Join(",", myItem.Names));

var myEmployee = new Employee();
//prints name1, name2
Console.WriteLine(String.Join(",", myEmployee.Names));