我在重构一段代码时遇到一个案例，该代码要求我在nodejs中使用对象工厂模式。因此，我在示例代码中尝试了这种模式，并提出了一些疑问。
factoryTest.js
var createFactory = require("./createFactory").createObjects();
var helloWorldObject = createFactory.helloWorld("userOne");
console.log("helloWorldObject: "+JSON.stringify(helloWorldObject));
var byeWorldObject = createFactory.byeWorld("userTwo", 22);
console.log("helloWorldObject: "+JSON.stringify(helloWorldObject));
console.log("byeWorldObject: "+JSON.stringify(byeWorldObject));
createFactory.js
var createObjects = function() {
console.log("received a request to create new object.")
this.localObject = {};
};
createObjects.prototype.helloWorld = function(name){
this.localObject = {}; // CASE 1 <<<--- how can this be removed?
this.localObject.name = name;
this.localObject.greeting = "Hello " +name;
return this.localObject;
};
createObjects.prototype.byeWorld = function(name, age){
this.localObject = {}; // CASE 2 <<<--- how can this be removed?
this.localObject.name = name;
this.localObject.age= age;
this.localObject.greeting = "Bye " +name;
return this.localObject;
};
exports.createObjects = function(){
return new createObjects();
}
CASE1和CASE2保持原样时的输出
received a request to create new object.
helloWorldObject: {"name":"userOne","greeting":"Hello userOne"}
helloWorldObject: {"name":"userOne","greeting":"Hello userOne"}
byeWorldObject: {"name":"userTwo","age":22,"greeting":"Bye userTwo"}
删除CASE1和CASE2时的输出
received a request to create new object.
helloWorldObject: {"name":"userOne","greeting":"Hello userOne"}
helloWorldObject: {"name":"userTwo","greeting":"Bye userTwo","age":22}
byeWorldObject: {"name":"userTwo","greeting":"Bye userTwo","age":22}
新版本：
createFactory.js
var objectFactory = function(){
console.log("received a new factory request.")
return new createObjects();
}
var createObjects = function() {
console.log("received a request to create new object.");
this.localObject = {};
};
createObjects.prototype.helloWorld = function(name){
this.localObject.name = name;
this.localObject.greeting = "Hello " +name;
return this.localObject;
};
createObjects.prototype.byeWorld = function(name, age){
this.localObject.name = name;
this.localObject.age = age;
this.localObject.greeting = "Bye " +name;
return this.localObject;
};
module.exports.objectFactory = objectFactory;
factoryTest.js
var createFactory = require("./createFactory").objectFactory;
var helloWorldObject = createFactory().helloWorld("userOne");
console.log("helloWorldObject: "+JSON.stringify(helloWorldObject));
var byeWorldObject = createFactory().byeWorld("userTwo", 22);
console.log("helloWorldObject: "+JSON.stringify(helloWorldObject));
console.log("byeWorldObject: "+JSON.stringify(byeWorldObject));
输出
received a new factory request.
received a request to create new object.
helloWorldObject: {"name":"userOne","greeting":"Hello userOne"}
received a new factory request.
received a request to create new object.
helloWorldObject: {"name":"userOne","greeting":"Hello userOne"}
byeWorldObject: {"name":"userTwo","age":22,"greeting":"Bye userTwo"}
这种方法能消除问题吗？
很高兴知道，该Factory模式实际上会创建对象。它不用于以任何方式重用它们。
如果要重用它们，则应使用所谓的object pool。
现在，您的代码中存在一些问题。一切都从这里开始：
exports.createObjects = function(){
return new createObjects();
}
因此，第一次使用时require("./createFactory").createObjects()，该函数将被执行并创建新工厂。现在，每次使用该工厂时，都将开始使用相同的对象- this.localObject。这意味着您没有项目的集合，而不是每次使用helloWorld或时都更改一个项目byeWorld。
this.localObject.name = name;
您实际上不是在创建新对象，而是使用已经创建的对象并更改其属性。如果您确实需要创建新对象，则类似以下内容可能会有所帮助：
function createObjects() {
this.objects = []; // store collection of objects
}
createObjects.prototype.helloWorld = function(name) {
var obj = {
name: name,
greeting: "Hello " + name
}
this.objects.push(obj);
return obj;
}
这将创建新对象，并且存储将随集合一起使用。如果要删除它，可以使用：
createObjects.prototype.removeObj = function(obj) {
var index = this.objects.indexOf(obj);
if (index != -1)
this.objects.splice(index, 1);
}
现在，您可以进行任何类型的功能以创建/删除不同的对象，它们将是具有不同属性的单独对象。
ps这种方法是拥有对象池的起点。但是，您必须使用不同的列表，或者至少为这些对象设置属性，说明是否使用了该对象。每次您要创建一个新对象时-检查是否有“自由”对象，如果存在，则将其返回。如果不是，请创建一个新的。
更新后，您实际上是在为所需的每个类创建新的工厂。每个工厂都包含一个对象，您可以通过在每个工厂上调用特定方法来修改该对象。尽管这可能对您有用，但这不是实际的工厂模式。为什么不在每次调用时都创建新对象（您不需要它们被单独的函数使用，对）？就像是：
createObjects.prototype.helloWorld = function(name) {
var result = {}; // CREATE brand new object
result.name = name;
result.greeting = "Hello " +name;
return result;
};
这样，您仍然可以将一个工厂与不同的对象一起使用：
var createFactory = require("./createFactory").objectFactory(); // create only ONCE
var helloWorldObject = createFactory.helloWorld("userOne");
// -> userOne
var byeWorldObject = createFactory.byeWorld("userTwo", 22);
// -> userTwo
helloWorldObj == byeWorldObj // -> false, different objects
本文收集自互联网，转载请注明来源。
如有侵权，请联系[email protected] 删除。
我来说两句