通过上面的分析，我们大致可以总结出工厂这种设计模式的应用场景：
（1）当一个类并不知道要创建的具体对象是什么，交由子类处理
（2）当一些类有相似的行为和结构，只是具体实现不同时，可以抽象出工厂
（3）使用者并不在乎具体类型，只在乎接口约定的行为，并且这种行为有个体差异
实例我借鉴了珲少的工程文档 首先，我们创建一个抽象的工程类，在其中创建一些私有的子类： 实现文件如下： 这样，我们的一个生产工厂就完成了，在外面，我们只需要知道一个类，我们的抽象父类，就可以实现个子类的行为，示例如下： 可以看到，对于开发者，我们并不知晓CarFactory类的存在，我们只需要通过TramsPortationFactory类，就能够操作各种交通工具，达到我们的需求。12345678910111213141516171819202122232425262728293031323334353637383940414243444546#import <Foundation/Foundation.h>//交通工具的枚举typedef enum {car,boat,airport,bycicle,bus,taxi}ToolsName;//代理 @protocol TransPortationDelegate <NSObject> -(void)toHome:(Class)class; @end//抽象工厂类 @interface TramsPortationFactory : NSObject+(TramsPortationFactory*)buyTool:(ToolsName)tool;//共有的方法接口 -(int)shouldPayMoney;-(void)run;@property(nonatomic,strong)id<TransPortationDelegate>delegate;@end//具体实现的子类@interface CarFactory : TramsPortationFactory @end@interface BoatFactory : TramsPortationFactory @end@interface AirportFactory : TramsPortationFactory @end@interface BycicleFactory : TramsPortationFactory @end@interface TaxiFactory : TramsPortationFactory @end@interface BusFactory : TramsPortationFactory @end12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091#import "TramsPortationFactory.h" @implementation TramsPortationFactory//实现的创建方法+(TramsPortationFactory*)buyTool:(ToolsName)tool{ switch (tool) { case car: return [[CarFactory alloc]init]; break; case airport: return [[AirportFactory alloc]init]; break; case bycicle: return [[BycicleFactory alloc]init]; break; case boat: return [[BoatFactory alloc]init]; break; case taxi: return [[TaxiFactory alloc]init]; break; case bus: return [[BusFactory alloc]init]; break; default: break; }} -(int)shouldPayMoney{ return 0;}-(void)run{ [self.delegate toHome:[self class]];}@end//各自类实现具体的行为@implementation CarFactory-(int)shouldPayMoney{ return 50;}-(void)run{ [super run]; NSLog(@"car to home");}@end@implementation AirportFactory-(int)shouldPayMoney{ return 1000;}-(void)run{ [super run]; NSLog(@"fly to home");}@end@implementation BoatFactory-(int)shouldPayMoney{ return 300;}-(void)run{ [super run]; NSLog(@"boat to home");}@end@implementation BusFactory-(int)shouldPayMoney{ return 10;}-(void)run{ [super run]; NSLog(@"bus to home");}@end@implementation BycicleFactory-(int)shouldPayMoney{ return 0;}-(void)run{ [super run]; NSLog(@"run to home");}@end@implementation TaxiFactory-(int)shouldPayMoney{ return 100;}-(void)run{ [super run]; NSLog(@"go to home");}@end12345678910111213141516- (void)viewDidLoad { [super viewDidLoad]; TramsPortationFactory * tool = [TramsPortationFactory buyTool:car]; tool.delegate=self; [tool run]; NSLog(@"花了:%d钱",[tool shouldPayMoney]); TramsPortationFactory * tool2 = [TramsPortationFactory buyTool:airport]; tool2.delegate=self; [tool2 run]; NSLog(@"花了:%d钱",[tool2 shouldPayMoney]); }-(void)toHome:(Class)class{ NSLog(@"%@",NSStringFromClass(class));}
原文：http://www.cnblogs.com/G-Flager/p/5304291.html