NSProxy 设计消息转发

@interface ViewController ()
@property (nonatomic, strong) NSTimer *timer;
@end

@implementation ViewController  
- (void)viewDidLoad {
    [super viewDidLoad];
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1 
			                  													target:self 
                                                selector:@selector(testForTimer)
                                                userInfo:nil
                                                 repeats:YES];
}

- (void)testForTimer {
    NSLog(@"%s",__func__);
}
@end

@interface SRProxy : NSProxy
@property (nonatomic, weak) id target;
+ (instancetype)proxyWithTarget:(id)target;
@end

@implementation SRProxy
+ (instancetype)proxyWithTarget:(id)target {
    SRProxy *proxy = [SRProxy alloc];
    proxy.target = target;
    return proxy;
}

- (id)forwardingTargetForSelector:(SEL)aSelector {
    if (self.target) {
        return self.target;
    }
    return self;
}

-(NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
    return [self.target  methodSignatureForSelector:aSelector];
}

- (void)forwardInvocation:(NSInvocation *)invocation {
    [invocation invokeWithTarget:self.target];
}
@end

self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:[SRProxy proxyWithTarget:self] selector:@selector(testForTimer) userInfo:nil repeats:YES];

@interface NSProxy <NSObject> {
    Class	isa;
}

 NSLog(@"isKindOfClass  == %d",[[SRProxy proxyWithTarget:self] isKindOfClass:[self class]]);

-(NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
    return [self.target  methodSignatureForSelector:aSelector];
}

- (void)forwardInvocation:(NSInvocation *)invocation {
	[invocation invokeWithTarget:self.target];
}