Analyze the JS abstract factory pattern for you in detail

This article mainly summarizes the author’s experience and summary when learning the JS abstract factory pattern. Friends who are interested can follow along and learn.

The following are the problems and code examples I encountered during my study. Finally, I will give you a summary of your learning about the JS abstract factory pattern.

The Abstract Factory pattern (Abstract Factory) uses class abstraction to make the business suitable for the creation of a product class cluster without being responsible for the instances of a certain type of product.

There is no direct abstract class in JS. Abstract is a reserved word, but it has not been implemented yet. Therefore, we need to throw an error in the class method to simulate the abstract class. If there is no override in the inherited subclass, If you write this method and call it, an error will be thrown.

const Car = function() { }
Car.prototype.getPrice = function() {return new Error('抽象方法不能调用')}

Implementation

There is an abstract factory pattern in object-oriented languages. First, declare an abstract class as a parent class to generalize a certain class. For the features required by the product, the subclass that inherits the parent class needs to implement the methods declared in the parent class and realize the functions declared in the parent class:

/**
* 实现subType类对工厂类中的superType类型的抽象类的继承
* @param subType 要继承的类
* @param superType 工厂类中的抽象类type
*/
const VehicleFactory = function(subType, superType) {
 if (typeof VehicleFactory[superType] === 'function') {
  function F() {
   this.type = '车辆'
  } 
  F.prototype = new VehicleFactory[superType]()
  subType.constructor = subType
  subType.prototype = new F()        // 因为子类subType不仅需要继承superType对应的类的原型方法，还要继承其对象属性
 } else throw new Error('不存在该抽象类')
}
VehicleFactory.Car = function() {
 this.type = 'car'
}
VehicleFactory.Car.prototype = {
 getPrice: function() {
  return new Error('抽象方法不可使用')
 },
 getSpeed: function() {
  return new Error('抽象方法不可使用')
 }
}
const BMW = function(price, speed) {
 this.price = price
 this.speed = speed
}
VehicleFactory(BMW, 'Car')    // 继承Car抽象类
BMW.prototype.getPrice = function() {    // 覆写getPrice方法
 console.log(`BWM price is ${this.price}`)
}
BMW.prototype.getSpeed = function() {
 console.log(`BWM speed is ${this.speed}`)
}
const baomai5 = new BMW(30, 99)
baomai5.getPrice()             // BWM price is 30
baomai5 instanceof VehicleFactory.Car    // true

Summary

Through the abstract factory, you can create products of a certain class cluster, and you can also check the product category through instanceof, and also have the necessary methods for this class cluster.

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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