［Objective-C 设计模式］工厂方法模式

工厂方法模式 : 定义一个用于创建对象的接口，让子类决定实例化哪一个类。工厂方法使一个类的实例化延迟到其子类。

优点

1、在工厂方法中，用户只需要知道所要产品的具体工厂，无须关心具体的创建过程，甚至不需要具体产品类的类名。

2、在系统增加新的产品时，我们只需要添加一个具体产品类和对应的实现工厂，无需对原工厂进行任何修改，很好地符合了“开闭原则”。

缺点

1、每次增加一个产品时，都需要增加一个具体类和对象实现工厂，是的系统中类的个数成倍增加，在一定程度上增加了系统的复杂度，同时也增加了系统具体类的依赖。这并不是什么好事。

2、大量的类暴露出来，需要自己去选择使用哪个工厂，使用起来过于繁琐。
总结

1、工厂方法模式完全符合“开闭原则”。

2、工厂方法模式使用继承，将对象的创建委托给子类，通过子类实现工厂方法来创建对象。

3、工厂方法允许类将实例化延伸到子类进行。

4、工厂方法让子类决定要实例化的类时哪一个。在这里我们要明白这并不是工厂来决定生成哪种产品，而是在编写创建者类时，不需要知道实际创建的产品是哪个，选择了使用哪个子类，就已经决定了实际创建的产品时哪个了。

5、在工厂方法模式中，创建者通常会包含依赖于抽象产品的代码，而这些抽象产品是、由子类创建的，创建者不需要真的知道在制作哪种具体产品。

项目地址：https://github.com/GameRisker/Study-Design-Patterns.git

//
//  main.m
//  FactoryMothed
//
//  Created by GameRisker on 16/1/3.
//  Copyright (c) 2016年 GameRisker. All rights reserved.
//

#import "ILeifeng.h"
#import "ILeifengFactory.h"
#import "UndergraduateFactory.h"
#import "VolunteerFactory.h"
#import <Foundation/Foundation.h>

int main(int argc, const char *argv[])
{
    @autoreleasepool
    {
        // insert code here...

        //        id<ILeifengFactory> factory = [[VolunteerFactory alloc] init];
        id<ILeifengFactory> factory = [[UndergraduateFactory alloc] init];
        id<ILeifeng> leifeng = [factory createLeifeng];

        [leifeng sweep];
        [leifeng wash];
        [leifeng buyRice];
    }
    return 0;
}

// main.m

// FactoryMothed

// Created by GameRisker on 16/1/3.

#import "ILeifeng.h"

#import "ILeifengFactory.h"

#import "UndergraduateFactory.h"

#import "VolunteerFactory.h"

#import <Foundation/Foundation.h>

int main(int argc, const char *argv[])

{

@autoreleasepool

{

// insert code here...

// id<ILeifengFactory> factory = [[VolunteerFactory alloc] init];

id<ILeifengFactory> factory = [[UndergraduateFactory alloc] init];

id<ILeifeng> leifeng = [factory createLeifeng];

[leifeng sweep];

[leifeng wash];

[leifeng buyRice];

}

return 0;

}

//
//  ILeifeng.h
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import <Foundation/Foundation.h>

@protocol ILeifeng <NSObject>

- (void)sweep;
- (void)wash;
- (void)buyRice;

@end

// ILeifeng.h

// Created by GameRisker on 16/1/3.

#import <Foundation/Foundation.h>

@protocol ILeifeng <NSObject>

- (void)sweep;

- (void)wash;

- (void)buyRice;

@end

//
//  Undergraduate.m
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "Undergraduate.h"

@implementation Undergraduate

- (void)sweep
{
    NSLog(@"Undergraduate help the elderly to sweep");
}

- (void)buyRice
{
    NSLog(@"Undergraduate help the elderly to buy rice");
}

- (void)wash
{
    NSLog(@"Undergraduate help the elderly wash");
}

@end

// Undergraduate.m

// Created by GameRisker on 16/1/3.

#import "Undergraduate.h"

@implementation Undergraduate

- (void)sweep

{

NSLog(@"Undergraduate help the elderly to sweep");

}

- (void)buyRice

{

NSLog(@"Undergraduate help the elderly to buy rice");

}

- (void)wash

{

NSLog(@"Undergraduate help the elderly wash");

}

@end

//
//  VolunteerFactory.m
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "VolunteerFactory.h"

@implementation VolunteerFactory

- (id<ILeifeng>)createLeifeng
{
    return [[Volunteer alloc] init];
}
@end

// VolunteerFactory.m

// Created by GameRisker on 16/1/3.

#import "VolunteerFactory.h"

@implementation VolunteerFactory

- (id<ILeifeng>)createLeifeng

{

return [[Volunteer alloc] init];

}

@end

//
//  VolunteerFactory.h
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "ILeifengFactory.h"
#import "Volunteer.h"
#import <Foundation/Foundation.h>
@interface VolunteerFactory : NSObject <ILeifengFactory>

@end

// VolunteerFactory.h

// Created by GameRisker on 16/1/3.

#import "ILeifengFactory.h"

#import "Volunteer.h"

#import <Foundation/Foundation.h>

@interface VolunteerFactory : NSObject <ILeifengFactory>

@end

//
//  ILeifengFactory.h
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "ILeifeng.h"
#import <Foundation/Foundation.h>

@protocol ILeifengFactory <NSObject>

- (id<ILeifeng>)createLeifeng;

@end

// ILeifengFactory.h

// Created by GameRisker on 16/1/3.

#import "ILeifeng.h"

#import <Foundation/Foundation.h>

@protocol ILeifengFactory <NSObject>

- (id<ILeifeng>)createLeifeng;

@end

//
//  UndergraduateFactory.m
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "UndergraduateFactory.h"

@implementation UndergraduateFactory

- (id<ILeifeng>)createLeifeng
{
    return [[Undergraduate alloc] init];
}

@end

// UndergraduateFactory.m

// Created by GameRisker on 16/1/3.

#import "UndergraduateFactory.h"

@implementation UndergraduateFactory

- (id<ILeifeng>)createLeifeng

{

return [[Undergraduate alloc] init];

}

@end

//
//  UndergraduateFactory.h
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "ILeifengFactory.h"
#import "Undergraduate.h"
#import <Foundation/Foundation.h>
@interface UndergraduateFactory : NSObject <ILeifengFactory>

@end

// UndergraduateFactory.h

// Created by GameRisker on 16/1/3.

#import "ILeifengFactory.h"

#import "Undergraduate.h"

#import <Foundation/Foundation.h>

@interface UndergraduateFactory : NSObject <ILeifengFactory>

@end

//
//  Undergraduate.h
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "ILeifeng.h"
#import <Foundation/Foundation.h>
@interface Undergraduate : NSObject <ILeifeng>

@end

// Undergraduate.h

// Created by GameRisker on 16/1/3.

#import "ILeifeng.h"

#import <Foundation/Foundation.h>

@interface Undergraduate : NSObject <ILeifeng>

@end

//
//  Volunteer.m
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "Volunteer.h"

@implementation Volunteer

- (void)sweep
{
    NSLog(@"Volunteer help the elderly to sweep");
}

- (void)buyRice
{
    NSLog(@"Volunteer help the elderly to buy rice");
}

- (void)wash
{
    NSLog(@"Volunteer help the elderly to wash");
}
@end

// Volunteer.m

// Created by GameRisker on 16/1/3.

#import "Volunteer.h"

@implementation Volunteer

- (void)sweep

{

NSLog(@"Volunteer help the elderly to sweep");

}

- (void)buyRice

{

NSLog(@"Volunteer help the elderly to buy rice");

}

- (void)wash

{

NSLog(@"Volunteer help the elderly to wash");

}

@end

//
//  Volunteer.h
//
//
//  Created by GameRisker on 16/1/3.
//
//

#import "ILeifeng.h"
#import <Foundation/Foundation.h>

@interface Volunteer : NSObject <ILeifeng>

@end

// Volunteer.h

// Created by GameRisker on 16/1/3.

#import "ILeifeng.h"

#import <Foundation/Foundation.h>

@interface Volunteer : NSObject <ILeifeng>

@end

参考：http://www.cnblogs.com/chenssy/（Java 版本）

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［Objective-C 设计模式］工厂方法模式

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