Objective-C命令模式

声明命令接口类

@protocol CommandProtocol <NSObject>

- (void)execute;

@end

声明&实现一个具体命令类

@interface ZDWLogNameConcreteCommand : NSObject <CommandProtocol>

- (instancetype)initWithReceiver:(ZDWUser *)receiver;

@end

@implementation ZDWLogNameConcreteCommand

- (instancetype)initWithReceiver:(ZDWUser *)receiver {
    if (self = [super init]) {
        self.user = receiver;
    }
    return self;
}

#pragma mark - CommandProtocol

- (void)execute {
    [self.user logName];
}

@end

命令接受者类

@interface ZDWUser : NSObject

- (void)logName;

@end

@implementation ZDWUser

- (void)logName {
    NSLog(@"%@",NSStringFromClass([ZDWUser class]));
}

@end

命令发送者类

@interface ZDWCommandInvoker : NSObject

@property (nonatomic, weak) id<CommandProtocol> command;

- (void)sendCommand;

@end

@implementation ZDWCommandInvoker

- (void)sendCommand {
    [self.command execute];
}

@end

Client

ZDWUser *user = [ZDWUser new];
    
    ZDWLogNameConcreteCommand *command = [[ZDWLogNameConcreteCommand alloc] initWithReceiver:user];
    ZDWCommandInvoker *invoker = [[ZDWCommandInvoker alloc] init];
    invoker.command = command;
    [invoker sendCommand];

如此便实现了命令发送者和接受者的完全解耦，二者只要通过命令对象来联系。不管接受者如何变化，只需要改变命令调用者的命令关联对象即可。客户端是面向命令调用者编程的，所以也不需要修改。