javascript设计模式-工厂模式（简单工厂）

Posted 2020-06-25 腾格里

接口在工厂模式中起着很重要的作用，如果不对对象进行某种类型检查的以确保其实现了必要的方法，工厂模式的好处也就所剩无几了，举个简单的例子。

Interface.js

 1 // Constructor.
 2 
 3 var Interface = function(name, methods) {
 4     if(arguments.length != 2) {
 5         throw new Error("Interface constructor called with " + arguments.length
 6           + "arguments, but expected exactly 2.");
 7     }
 8     
 9     this.name = name;
10     this.methods = [];
11     for(var i = 0, len = methods.length; i < len; i++) {
12         if(typeof methods[i] !== ‘string‘) {
13             throw new Error("Interface constructor expects method names to be " 
14               + "passed in as a string.");
15         }
16         this.methods.push(methods[i]);        
17     }    
18 };    
19 
20 // Static class method.
21 
22 Interface.ensureImplements = function(object) {
23     if(arguments.length < 2) {
24         throw new Error("Function Interface.ensureImplements called with " + 
25           arguments.length  + "arguments, but expected at least 2.");
26     }
27 
28     for(var i = 1, len = arguments.length; i < len; i++) {
29         var interface = arguments[i];
30         if(interface.constructor !== Interface) {
31             throw new Error("Function Interface.ensureImplements expects arguments "   
32               + "two and above to be instances of Interface.");
33         }
34         
35         for(var j = 0, methodsLen = interface.methods.length; j < methodsLen; j++) {
36             var method = interface.methods[j];
37             if(!object[method] || typeof object[method] !== ‘function‘) {
38                 throw new Error("Function Interface.ensureImplements: object " 
39                   + "does not implement the " + interface.name 
40                   + " interface. Method " + method + " was not found.");
41             }
42         }
43     } 
44 };

View Code

声明一个接口Bicycle，定义该接口应该有哪些方法

1 var Bicycle = new Interface("Bicycle",["assemble","wash","ride","repair"]);

构造一个简单的工厂BicycleShop，根据传递的模型，卖出不同类型的自行车。

 1 var BicycleShop  = function(){};
 2     
 3     BicycleShop.prototype = {
 4         sellBicycle:function(model){
 5             var bicycle;
 6             switch(model){
 7                 case "The Speedster":
 8                     bicycle = new Speedster();
 9                     break;
10                 case "The Lowrider":
11                     bicycle = new Lowrider();
12                     break;
13                 case "The Comfort Cruiser":
14                 default:
15                     bicycle = new ComfortCruiser();
16             }
17             Interface.ensureImplements(bicycle,Bicycle);
18             bicycle.assemble();
19             bicycle.wash();
20             return bicycle;
21         }
22     }

建立一个Speedster类型的自行车，且该类提供了必要的方法

 1 var Speedster = function(){
 2     };
 3     Speedster.prototype = {
 4         assemble:function(){
 5             console.log("assemble method is exected");
 6         },
 7         wash:function(){
 8             console.log("wash method is exected");
 9         },
10         ride:function(){
11             console.log("ride method is exected");
12         },
13         repair:function(){
14             console.log("repair method is exected");
15         }
16     }

创建一个工厂，传入模型参数

1 var californiaCruisers = new BicycleShop();
2 californiaCruisers.sellBicycle("The Speedster");

结果：