［Objective-C 设计模式］外观模式

外观模式：为子系统中的一组接口提供一个一致的界面，此模式定义了一个高层接口，这个接口使得这一子系统更加容易使用。

优点：
1、降低了模块与模块之间的依赖，完美地体现了依赖倒转原则和迪米特法则的思想
2、只是提供了一个访问子系统的统一入口，并不影响用户直接使用子系统类
3、降低了大型软件系统中的编译依赖性，并简化了系统在不同平台之间的移植过程

缺点：

1、不能很好地限制客户使用子系统类，如果对客户访问子系统类做太多的限制则减少了可变性和灵活性
2、在不引入抽象外观类的情况下，增加新的子系统可能需要修改外观类或客户端的源代码，违背了“开闭原则”

模式总结
1、外观模式的主要优点就在于减少了系统与系统之间的关联对象，使用客户对子系统的使用变得简单了，也实现了客户与子系统之间的松耦合关系。它的缺点就在于违背了“开闭原则”。
2、如果需要实现一个外观模式，需要将子系统组合进外观中，然后将工作委托给子系统执行。

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

//
//  main.m
//  Facade
//
//  Created by GameRisker on 16/1/24.
//  Copyright (c) 2016年 GameRisker. All rights reserved.
//

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

int main(int argc, const char *argv[])
{
    @autoreleasepool
    {
        // insert code here...
        Facade *facade = [[Facade alloc] init];
        [facade MothedA];
        [facade MothedB];
    }
    return 0;
}

// main.m

// Facade

// Created by GameRisker on 16/1/24.

#import "Facade.h"

#import <Foundation/Foundation.h>

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

{

@autoreleasepool

{

// insert code here...

Facade *facade = [[Facade alloc] init];

[facade MothedA];

[facade MothedB];

}

return 0;

}

//
//  Facade.h
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import "SubSystemFour.h"
#import "SubSystemOne.h"
#import "SubSystemThree.h"
#import "SubSystemTwo.h"
#import <Foundation/Foundation.h>

@interface Facade : NSObject

@property(strong, nonatomic) SubSystemOne *m_subOne;
@property(strong, nonatomic) SubSystemTwo *m_subTwo;
@property(strong, nonatomic) SubSystemThree *m_subThree;
@property(strong, nonatomic) SubSystemFour *m_subFour;

- (void)MothedA;
- (void)MothedB;

@end

// Facade.h

// Created by GameRisker on 16/1/24.

#import "SubSystemFour.h"

#import "SubSystemOne.h"

#import "SubSystemThree.h"

#import "SubSystemTwo.h"

#import <Foundation/Foundation.h>

@interface Facade : NSObject

@property(strong, nonatomic) SubSystemOne *m_subOne;

@property(strong, nonatomic) SubSystemTwo *m_subTwo;

@property(strong, nonatomic) SubSystemThree *m_subThree;

@property(strong, nonatomic) SubSystemFour *m_subFour;

- (void)MothedA;

- (void)MothedB;

@end

//
//  Facade.m
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import "Facade.h"

@implementation Facade

- (instancetype)init
{
    if (self = [super init])
    {
        self.m_subOne = [[SubSystemOne alloc] init];
        self.m_subTwo = [[SubSystemTwo alloc] init];
        self.m_subThree = [[SubSystemThree alloc] init];
        self.m_subFour = [[SubSystemFour alloc] init];
    }

    return self;
}

- (void)MothedA
{
    [self.m_subOne MethodOne];
    [self.m_subTwo MethodTwo];
    [self.m_subThree MethodThree];
}

- (void)MothedB
{
    [self.m_subOne MethodOne];
    [self.m_subTwo MethodTwo];
    [self.m_subFour MethodFour];
}

@end

// Facade.m

// Created by GameRisker on 16/1/24.

#import "Facade.h"

@implementation Facade

- (instancetype)init

{

if (self = [super init])

{

self.m_subOne = [[SubSystemOne alloc] init];

self.m_subTwo = [[SubSystemTwo alloc] init];

self.m_subThree = [[SubSystemThree alloc] init];

self.m_subFour = [[SubSystemFour alloc] init];

}

return self;

}

- (void)MothedA

{

[self.m_subOne MethodOne];

[self.m_subTwo MethodTwo];

[self.m_subThree MethodThree];

}

- (void)MothedB

{

[self.m_subOne MethodOne];

[self.m_subTwo MethodTwo];

[self.m_subFour MethodFour];

}

@end

//
//  SubSystemOne.h
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import <Foundation/Foundation.h>

@interface SubSystemOne : NSObject

- (void)MethodOne;

@end

// SubSystemOne.h

// Created by GameRisker on 16/1/24.

#import <Foundation/Foundation.h>

@interface SubSystemOne : NSObject

- (void)MethodOne;

@end

//
//  SubSystemOne.m
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import "SubSystemOne.h"

@implementation SubSystemOne

- (void)MethodOne
{
    NSLog(@"execution Method One.");
}
@end

// SubSystemOne.m

// Created by GameRisker on 16/1/24.

#import "SubSystemOne.h"

@implementation SubSystemOne

- (void)MethodOne

{

NSLog(@"execution Method One.");

}

@end

//
//  SubSystemTwo.h
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import <Foundation/Foundation.h>

@interface SubSystemTwo : NSObject

- (void)MethodTwo;

@end

// SubSystemTwo.h

// Created by GameRisker on 16/1/24.

#import <Foundation/Foundation.h>

@interface SubSystemTwo : NSObject

- (void)MethodTwo;

@end

//
//  SubSystemTwo.m
//  
//
//  Created by GameRisker on 16/1/24.
//
//

#import "SubSystemTwo.h"

@implementation SubSystemTwo

- (void)MethodTwo
{
    NSLog(@"execution Method Two.");
}

@end

// SubSystemTwo.m

// Created by GameRisker on 16/1/24.

#import "SubSystemTwo.h"

@implementation SubSystemTwo

- (void)MethodTwo

{

NSLog(@"execution Method Two.");

}

@end

//
//  SubSystemThree.h
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import <Foundation/Foundation.h>

@interface SubSystemThree : NSObject

- (void)MethodThree;

@end

// SubSystemThree.h

// Created by GameRisker on 16/1/24.

#import <Foundation/Foundation.h>

@interface SubSystemThree : NSObject

- (void)MethodThree;

@end

//
//  SubSystemThree.m
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import "SubSystemThree.h"

@implementation SubSystemThree

- (void)MethodThree
{
    NSLog(@"execution Method Three.");
}

@end

// SubSystemThree.m

// Created by GameRisker on 16/1/24.

#import "SubSystemThree.h"

@implementation SubSystemThree

- (void)MethodThree

{

NSLog(@"execution Method Three.");

}

@end

//
//  SubSystemFour.h
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import <Foundation/Foundation.h>

@interface SubSystemFour : NSObject

- (void)MethodFour;

@end

// SubSystemFour.h

// Created by GameRisker on 16/1/24.

#import <Foundation/Foundation.h>

@interface SubSystemFour : NSObject

- (void)MethodFour;

@end

//
//  SubSystemFour.m
//
//
//  Created by GameRisker on 16/1/24.
//
//

#import "SubSystemFour.h"

@implementation SubSystemFour

- (void)MethodFour
{
    NSLog(@"execution Method Four.");
}

@end

// SubSystemFour.m

// Created by GameRisker on 16/1/24.

#import "SubSystemFour.h"

@implementation SubSystemFour

- (void)MethodFour

{

NSLog(@"execution Method Four.");

}

@end

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

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［Objective-C 设计模式］外观模式

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