iOS 定时器01

@interface MLProxy ()
@property (nonatomic, weak) id target;
@end

@implementation MLProxy

+ (instancetype)createProxyWeithTarget:(id)target{
   MLProxy *proxy = [self alloc];
    proxy.target = target;
    return proxy;
}

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

@end

- (void)viewDidLoad {
    [super viewDidLoad];
    self.proxy = [MLProxy createProxyWeithTarget:self];
    // NSTimer
    // 由于iOS的消息机制（objc_msgSend()）, 系统会对self.proxy 发送一个scheduledTimerWithTimeInterval的消息由于MLProxyb并没有实现该方法，就会执行Runtime的消息转发机制。
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self.proxy selector:@selector(timerAction) userInfo:nil repeats:YES];
}

自己创建的中间项
.h

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface XDProxy : NSProxy
/**
 *  代理的对象
 */
@property (nonatomic,weak)id obj;
@end

NS_ASSUME_NONNULL_END

.m

#import "XDProxy.h"

@implementation XDProxy

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector{
    NSMethodSignature *sig = nil;
    sig = [self.obj methodSignatureForSelector:aSelector];
    return sig;
}

/**
 *  NSInvocation封装了NSMethodSignature，通过invokeWithTarget方法将消息转发给其他对象.这里转发给控制器执行。
 */
- (void)forwardInvocation:(NSInvocation *)anInvocation{
    [anInvocation invokeWithTarget:self.obj];
}

@end