从类调用方法而不实例化它 [英] call method from class without instantiate it

问题描述

我会尽力澄清 例如，如果您使用像cocos2d-x这样的框架

i will try to make it clear as i can if you look to frameworks like cocos2d-x for example

cc.Sprite.extend();

这里的Sprite是类，我们如何在不使用new关键字

Sprite here is class how we can call method without instantiate it with new keyword

我有一个类，例如

var superClass = function(){

    this.init = function(){
        console.log("new class constructed !")
    };

};

要调用init，我必须这样做

to call init i must do this

obj = new superClass();
obj.init();

但是如何在不实例化类的情况下引用方法

but How can I reference a method a class without instantiating it

推荐答案

基本上，您想要的是静态方法.有多种方法可以实现这一目标.我认为，使用对象文字可以为您轻松完成.

Basically what you want is a static method. There are different ways to achieve that. I think, using an object literal would the easier thing to do for you.

乱扔物体:

var superClass = {
    init: function(){
        console.log("new class constructed !")
    }
};

superClass.init();

https://jsfiddle.net/ckgmb9fk/

但是，您仍然可以使用函数构造函数定义对象，然后将静态方法添加到类".例如，您可以执行以下操作:

However, you can still define an object using a function constructor and then add a static method to the "class". For example you can do this:

var SuperClass = function(){};

SuperClass.prototype.methodA = function() {
    console.log("methodA");
};

SuperClass.init = function() {
    console.log("Init function");
}

SuperClass.init();

var sc = new SuperClass();
sc.methodA();

请注意，方法init在SuperClass实例对象中将不可用，因为它在对象原型中不可用.

Note, the method init won't be available in the SuperClass instance object as it is not in the object prototype.

https://jsfiddle.net/mLxoh1qj/

扩展原型:

var SuperClass = function(){};

  SuperClass.prototype.init = function() {
      console.log("Init");
  };

SuperClass.prototype.init();

var sc = new SuperClass();
sc.init();

https://jsfiddle.net/0ayct1ry/

如果要从SuperClass原型和对象实例访问函数init，则此解决方案很有用.

This solution is useful if you want to access the function init both from the SuperClass prototype and from an object instance.

ES6:

这在ES6中要好得多

class SuperClass {
   static init() {
     console.log("new class constructed !")
   }
}

SuperClass.init();

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