JavaScript 设计模式学习 Factory

/* 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. */

var alecsCruisers = new AcmeBicycleShop(); 
var yourNewBike = alecsCruisers.sellBicycle('The Lowrider'); 
var bobsCruisers = new GeneralProductsBicycleShop(); 
var yourSecondNewBike = bobsCruisers.sellBicycle('The Lowrider');