动态实例化传递参数

Question

我运行遇到了从不同的 class 动态生成对象实例的问题。所以我有一个返回产品数组的服务器响应，这些产品的类型各不相同，这将因要使用的实例化 class 以及传递给构造函数的参数而异。

在下面的示例中，我有一个根 class Product，它由 class Food 和 classFurniture 扩展，这些扩展 class 的参数各不相同，需要插入他们的亲戚constructors()。

我正在使用产品属性 product.metaType 来保存有关 class 在实例化中使用的信息。

//root product class which all inherit from
class Product{
 constructor(price){
  this.price = price;
  this.quantity = null;
 } 
}
//food product class
class Food extends Product{
 constructor(price,exp){
  super(price);
  this.expiration = exp;
 } 
}
//furniture product class
class Furniture extends Product{
 constructor(price,dimensions){
  this.price = price; 
  this.dimensions = dimensions; 
 } 
}
class Chair extends Furniture{
 constructor(price,dimensions,type){
  super(price,dimensions);
  this.type = type;
 }
}
class Pizza extends Food{
 constructor(price,exp,type){
  super(price,exp);
  this.type = type;
 }
}
class Cookies extends Food{
 constructor(price,exp,type){
  super(price,exp);
  this.type = type;
 }
}
class IceCream extends Food{
 constructor(price,exp,type){
  super(price,exp);
  this.type = type;
 }
}
//init (iife)
(()=>{ 
 //list of products emulated from a server response
 var products:[
  {
   metaType: "Pizza",
   name: "digiorno",
   price: 20,
   type: "pepperoni",
   exp: new Date()
  },
  {
   metaType: "Chair",
   name: "Lazy Boy",
   price: 400,
      dimensions:{
      height: 4,
      width: 2,
     length: 6
      },
   type: "modern"
  },
  {
   metaType: "Cookies",
   name: "Mrs. Fields",
   price: 10,
   type: "chocolate chip",
   exp: new Date()
  },
  {
   metaType: "IceCream",
   name: "Ben & Jerry's",
   price: 15,
   type: "half baked",
   exp: new Date()
  }
 ]; 
 var storeProducts = [];
 //loop through products array
 products.forEach((item)=>{
  //create new instance of the specific product, append to the 'storeProducts' array
  //each product contains a metaType property which is the CLASS to use
        //how can I dynamically do this?
  storeProducts.push(new window[item.metaType]());
 });
})();

问题：如何动态实例化不同的class并传递参数？

Answer 1

创建 name -> constructor 地图。 classes 不会成为全局对象的属性：

const cls = {Food, Furniture, ...};

让构造函数接受一个参数并解构它，例如

class Food extends Product{
  constructor({price,exp}){
      //      ^         ^    destructuring
      super(price);
      this.expiration = exp;
  } 
}

然后你可以将整个对象传递给构造函数：

 new cls[item.metaType](item);

动态实例化传递参数

Dynamic instantiations passing parameters

javascript

ecmascript-6

es6-class