iOS架构师_桥接模式

桥接模式定义：

将抽象部分与它的实现部分分离，使它们都可以独立的变化。
原理：抽象层与实现层相分离，抽象层定义了供客户端调用的抽象接口，实现层提供了具体的逻辑，实现类的引用被封装到抽象层的实例中，桥接就此形成。

原始代码示例：

首先创建两个类：XiaoMiRemote(小米遥控器) XiaoMiTV(小米电视)

XiaoMiTV.h

#import <Foundation/Foundation.h>

@interface XiaoMiTV : NSObject
// 电视提供给外界的接口
- (void)loadCommand:(NSString *)command;
@end

XiaoMiTV.m

#import "XiaoMiTV.h"

@implementation XiaoMiTV
- (void)loadCommand:(NSString *)command {
    // 点击之后, 实现的业务逻辑
    NSLog(@"您按的是:----%@",command);
}
@end

XiaoMiRemote.h

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

@interface XiaoMiRemote : NSObject
@property (nonatomic, strong) XiaoMiTV *TV;

// 方向控制
- (void)up;
- (void)down;
- (void)left;
- (void)right;
@end

XiaoMiRemote.m

#import "XiaoMiRemote.h"

@implementation XiaoMiRemote
- (void)up {
    [self.TV loadCommand:@"up"];
}
- (void)down {
    [self.TV loadCommand:@"down"];

}
- (void)left {
    [self.TV loadCommand:@"left"];

}
- (void)right {
    [self.TV loadCommand:@"right"];

}
@end

按照上面的操作，再次创建KJRemote,KJTV

KJRemote.h

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

@interface KJRemote : NSObject
@property (nonatomic, strong) KJTV *TV;

// 方向控制
- (void)up;
- (void)down;
- (void)left;
- (void)right;

- (void)action1;
- (void)action2;

@end

KJRemote.m

#import "KJRemote.h"

@implementation KJRemote
- (void)up {
    [self.TV loadCommandKJ:@"up"];
}
- (void)down {
    [self.TV loadCommandKJ:@"down"];

}
- (void)left {
    [self.TV loadCommandKJ:@"left"];

}
- (void)right {
    [self.TV loadCommandKJ:@"right"];

}

- (void)action1 {
    [self.TV loadCommandKJ:@"action1"];

}
- (void)action2 {
    [self.TV loadCommandKJ:@"action2"];

};
@end

KJTV.h

#import <Foundation/Foundation.h>

@interface KJTV : NSObject
// 电视提供给外界的接口
- (void)loadCommandKJ:(NSString *)command;
@end

KJTV.m

#import "KJTV.h"

@implementation KJTV
- (void)loadCommandKJ:(NSString *)command {
    // 点击之后, 实现的业务逻辑
    NSLog(@"您按的是KJ:----%@",command);
}
@end

ViewController.m

#import "ViewController.h"
#import "XiaoMiTV.h"
#import "XiaoMiRemote.h"
#import "KJTV.h"
#import "KJRemote.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    XiaoMiTV *TV = [[XiaoMiTV alloc] init];
    XiaoMiRemote *remote = [[XiaoMiRemote alloc] init];
    remote.TV = TV;
    [remote up];

    KJTV *TV2 = [[KJTV alloc] init];
    KJRemote *remote2 = [[KJRemote alloc] init];
    remote2.TV = TV2;
    [remote2 action1];
    [remote2 up];

}

@end

可是我们可以把康佳的电视，交给小米的遥控器去控制嘛？

答案肯定是不可以，我们使用桥接模式，把它们共同的点去抽取出来。

桥接抽取

思路: 把遥控器抽象出一个父类, 把电视机也抽象出一个父类
用抽象的遥控器对抽象电视机类进行引用,具体的实现由他们的子类来做

首先创建两个抽象的父类，Remote,TV

TV.h

#import <Foundation/Foundation.h>

@interface TV : NSObject
// 电视机提供给外界调用的一个方法
- (void)loadCommand:(NSString *)command;

@end

TV.m

#import "TV.h"

@implementation TV
- (void)loadCommand:(NSString *)command {}
@end

Remote.h

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

@interface Remote : NSObject
@property (nonatomic, strong) TV *tv;

- (void)setCommand:(NSString *)commmand;
@end

Remote.m

#import "Remote.h"

@implementation Remote
- (void)setCommand:(NSString *)commmand {
    [self.tv loadCommand:commmand];
}
@end

创建继承自Remote的子类SubRemote
SubRemote.h

#import "Remote.h"
//这种不改变父类的方法，由子类去拓展方法的实现，符合开闭原则
@interface SubRemote : Remote
// 方向控制
- (void)up;
- (void)down;
- (void)left;
- (void)right;
@end

SubRemote.m

#import "SubRemote.h"

@implementation SubRemote
// 方向控制
- (void)up {
    [super setCommand:@"up"];
}
- (void)down {
    [super setCommand:@"down"];

}
- (void)left {
    [super setCommand:@"left"];

}
- (void)right {
    [super setCommand:@"right"];

}
@end

创建继承自TV的TVXiaoMI和TVKJ

TVXiaoMI.m

#import "TVXiaoMI.h"

@implementation TVXiaoMI
- (void)loadCommand:(NSString *)command {

    if ([command isEqualToString:@"up"]) {
        NSLog(@"您按的是XM:----%@",command);
    }
    else if ([command isEqualToString:@"down"]){
        NSLog(@"您按的是XM:----%@",command);
    }
    else if ([command isEqualToString:@"left"]){
        NSLog(@"您按的是XM:----%@",command);
    }
    else if ([command isEqualToString:@"right"]){
        NSLog(@"您按的是XM:----%@",command);
    }
    else {
        NSLog(@"超出范围");
    }
}

@end

TVKJ.m

#import "TVKJ.h"

@implementation TVKJ
- (void)loadCommand:(NSString *)command {

    if ([command isEqualToString:@"up"]) {
        NSLog(@"您按的是KJ:----%@",command);
    }
    else if ([command isEqualToString:@"down"]){
        NSLog(@"您按的是KJ:----%@",command);
    }
    else if ([command isEqualToString:@"left"]){
        NSLog(@"您按的是KJ:----%@",command);
    }
    else if ([command isEqualToString:@"right"]){
        NSLog(@"您按的是KJ:----%@",command);
    }
    else {
        NSLog(@"超出范围");
    }
}
@end

ViewController.m

#import "ViewController.h"
#import "XiaoMiTV.h"
#import "XiaoMiRemote.h"
#import "KJTV.h"
#import "KJRemote.h"

#import "SubRemote.h"
#import "TVKJ.h"
#import "TVXiaoMI.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // 遥控器调用康佳电视
    SubRemote *subremote = [[SubRemote alloc] init];
    subremote.tv = [[TVKJ alloc] init];
    [subremote up];

    // 遥控器来调用小米
    subremote.tv = [[TVXiaoMI alloc] init];
    [subremote up];
    [subremote down];
}

@end

桥接模式的特点:
1. 将依赖具体的实现,改为依赖抽象. 得到松耦合的状态
2. 分离了接口和实现部分
3. 提高了扩展性.