1 @interface XXClass : NSObject
 2 - (void)start;
 3 - (void)stop;
 4 @end
 5
 6 @implementation XXClass {
 7     NSTimer *timer;
 8 }
 9
10 - (id)init {
11     return [super init];
12 }
13
14 - (void)dealloc {
15     [timer]
16 }
17
18 - (void)stop {
19     [timer invalidate];
20     timer = nil;
21 }
22
23 - (void)start {
24     timer = [NSTimerscheduledTimerWithTimeInterval:5.0
25                                             target:self
26                                           selector:selector(doSomething)
27                                           userInfo:nil
28                                            repeats:YES];
29 }
30
31 - (void)doSomething {
32     //doSomething
33 }
34
35 @end

 1 @interface NSTimer (XXBlocksSupport)
 2
 3 + (NSTimer *)xx_scheduledTimerWithTimeInterval:(NSTimeInterval)interval
 4                                          block:(void(^)())block
 5                                        repeats:(BOOL)repeats;
 6
 7 @end
 8
 9 @implementation NSTimer (XXBlocksSupport)
10
11 + (NSTimer *)xx_scheduledTimerWithTimeInterval:(NSTimeInterval)interval
12                                          block:(void(^)())block
13                                        repeats:(BOOL)repeats
14 {
15     return [self scheduledTimerWithTimeInterval:interval
16                                           target:self
17                                         selector:@selector(xx_blockInvoke:)
18                                         userInfo:[block copy]
19                                          repeats:repeats];
20 }
21
22 + (void)xx_blockInvoke:(NSTimer *)timer {
23     void (^block)() = timer.userinfo;
24     if(block) {
25         block();
26     }
27 }
28
29 @end
30 //调用
31 - (void)start {
32     __weak XXClass *weakSelf = self;
33     timer = [NSTimer xx_scheduledTimerWithTimeInterval:.5
34                                                  block:^{
35                                                  XXClass *strongSelf = weakSelf;
36                                                  [strongSelf doSomething];
37                                                         }
38                                                repeats:YES];
39 }

1 //当一个消息转发的动作NSInvocation到来的时候，在这里选择把消息转发给对应的实际处理对象
2 - (void)forwardInvocation:(NSInvocation *)anInvocation
3
4 //当一个SEL到来的时候，在这里返回SEL对应的NSMethodSignature
5 - (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
6
7 //是否响应一个SEL
8 + (BOOL)respondsToSelector:(SEL)aSelector

1 //消息转发第一步，在这里可以动态的为类添加方法，这样类自己就能处理了
2 ＋resolveInstanceMethod:
3 //消息转发第二步，在第一步无法完成的情况下执行。这里只是把一个Selector简单的转发给另一个对象
4 - forwardingTargetForSelector:
5 //消息转发第三步，在第二步也无法完成的情况下执行。将整个消息封装成NSInvocation，传递下去
6 - forwardInvocation:

@interface WeakProxy : NSProxy
@property (weak,nonatomic,readonly)id target;
+ (instancetype)proxyWithTarget:(id)target;
- (instancetype)initWithTarget:(id)target;
@end@implementation WeakProxy
- (instancetype)initWithTarget:(id)target{_target = target;return self;
}
+ (instancetype)proxyWithTarget:(id)target{return [[self alloc] initWithTarget:target];
}
- (void)forwardInvocation:(NSInvocation *)invocation{SEL sel = [invocation selector];if ([self.target respondsToSelector:sel]) {[invocation invokeWithTarget:self.target];}
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector{return [self.target methodSignatureForSelector:aSelector];
}
- (BOOL)respondsToSelector:(SEL)aSelector{return [self.target respondsToSelector:aSelector];
}
@end

  self.timer = [NSTimer timerWithTimeInterval:1target:[WeakProxy proxyWithTarget:self]selector:@selector(timerInvoked:)userInfo:nilrepeats:YES];