消息转发示例

ObjcForwarding.m

//Person 本身没有实现 sayHello， 转发到内部实例中。
@interface Person : NSObject

- (void) sayHello;


@end

@implementation Person {
    
    InternalPerson *_iPerson;
    
}

- (instancetype)init {
    
    self = [super init];
    
    if(self) {
        
        _iPerson = [[InternalPerson alloc] init];
        
    }
    
    return self;
    
}

- (void)forwardInvocation:(NSInvocation *)anInvocation
{
    //转发消息
    [anInvocation invokeWithTarget:_iPerson];
    
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
    
    //返回消息签名
    NSMethodSignature* signature = [super methodSignatureForSelector:aSelector];
    if (!signature) {
        signature = [_iPerson methodSignatureForSelector:aSelector];
    }
    return signature;
    
}

@end



//InternalPerson 为实际的消息接收实例
@interface InternalPerson : NSObject

- (void) sayHello;

@end

@implementation InternalPerson

- (void)sayHello {
    
    //实际的消息接受者
    NSLog(@"hello world");
    
}

@end

//程序入口
int main() {

    Person *person = [[Person alloc] init];
    [person sayHello];

}