JavaScript 设计模式学习 Factory

复制代码代码如下:
/* DisplayModule interface. */
var DisplayModule = new Interface（"DisplayModule", ["append", "remove", "clear"]）;
/* ListDisplay class. */
//通过接口实现工厂，这是通过List方式显示RSS
var ListDisplay = function（id, parent） { // implements DisplayModule
this.list = document.createElement（"ul"）;
this.list.id = id;
parent.appendChild（this.list）;
};
ListDisplay.prototype = {
append: function（text） {
var newEl = document.createElement（"li"）;
this.list.appendChild（newEl）;
newEl.innerHTML = text;
return newEl;
},
remove: function（el） {
this.list.removeChild（el）;
},
clear: function（） {
this.list.innerHTML = "";
}
};
/* Configuration object. */
var conf = {
id: "cnn-top-stories",
feedUrl: "http://rss.cnn.com/rss/cnn_topstories.rss",
updateInterval: 60, // In seconds.
parent: $（"feed-readers"）
};
/* FeedReader class. */
var FeedReader = function（display, xhrHandler, conf） {
this.display = display;
this.xhrHandler = xhrHandler;
this.conf = conf;
this.startUpdates（）;
};
FeedReader.prototype = {
fetchFeed: function（） {
var that = this;
var callback = {
success: function（text, xml） { that.parseFeed（text, xml）; },
failure: function（status） { that.showError（status）; }
};
this.xhrHandler.request（"GET", "feedProxy.php？feed=" + this.conf.feedUrl,
callback）;
},
parseFeed: function（responseText, responseXML） {
this.display.clear（）;
var items = responseXML.getElementsByTagName（"item"）;
for（var i = 0, len = items.length; i < len; i++） {
var title = items[i].getElementsByTagName（"title"）[0];
var link = items[i].getElementsByTagName（"link"）[0];
this.display.append（"<a href="" + link.firstChild.data + "">" +
title.firstChild.data + "</a>"）;
}
},
showError: function（statusCode） {
this.display.clear（）;
this.display.append（"Error fetching feed."）;
},
stopUpdates: function（） {
clearInterval（this.interval）;
},
startUpdates: function（） {
this.fetchFeed（）;
var that = this;
this.interval = setInterval（function（） { that.fetchFeed（）; },
this.conf.updateInterval * 1000）;
}
};
/* FeedManager namespace. */
//工厂管理器，这里可以根据传进来的参数选择具体的Display
var FeedManager = {
createFeedReader: function（conf） {
var displayModule = new ListDisplay（conf.id + "-display", conf.parent）;
Interface.ensureImplements（displayModule, DisplayModule）;
var xhrHandler = XhrManager.createXhrHandler（）;
Interface.ensureImplements（xhrHandler, AjaxHandler）;
return new FeedReader（displayModule, xhrHandler, conf）;
}
};
=====================================================
另一个自行车工厂的例子：
var BicycleShop = function（） {};
BicycleShop.prototype = {
sellBicycle: function（model） {
var bicycle = this.createBicycle（model）;
bicycle.assemble（）;
bicycle.wash（）;
return bicycle;
},
createBicycle: function（model） {
throw new Error（"Unsupported operation on an abstract class."）;
}
};
/* AcmeBicycleShop class. */
var AcmeBicycleShop = function（） {};
extend（AcmeBicycleShop, BicycleShop）;
AcmeBicycleShop.prototype.createBicycle = function（model） {
var bicycle;
switch（model） {
case "The Speedster":
bicycle = new AcmeSpeedster（）;
break;
case "The Lowrider":
bicycle = new AcmeLowrider（）;
break;
case "The Flatlander":
bicycle = new AcmeFlatlander（）;
break;
case "The Comfort Cruiser":
default:
bicycle = new AcmeComfortCruiser（）;
}
Interface.ensureImplements（bicycle, Bicycle）;
return bicycle;
};
/* GeneralProductsBicycleShop class. */
var GeneralProductsBicycleShop = function（） {};
extend（GeneralProductsBicycleShop, BicycleShop）;
GeneralProductsBicycleShop.prototype.createBicycle = function（model） {
var bicycle;
switch（model） {
case "The Speedster":
bicycle = new GeneralProductsSpeedster（）;
break;
case "The Lowrider":
bicycle = new GeneralProductsLowrider（）;
break;
case "The Flatlander":
bicycle = new GeneralProductsFlatlander（）;
break;
case "The Comfort Cruiser":
default:
bicycle = new GeneralProductsComfortCruiser（）;
}
Interface.ensureImplements（bicycle, Bicycle）;
return bicycle;
};

/* Usage. */
复制代码代码如下:
var alecsCruisers = new AcmeBicycleShop（）;
var yourNewBike = alecsCruisers.sellBicycle（"The Lowrider"）;
var bobsCruisers = new GeneralProductsBicycleShop（）;
var yourSecondNewBike = bobsCruisers.sellBicycle（"The Lowrider"）;