iOS 关于定时器NSTimer

一、默认就会执行 ，是在 NSDefaultRunLoopMode 模式下运行的 。如果滑动会切换 UITrackingRunLoopMode  定时器失效。

 [NSTimer scheduledTimerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
        NSLog(@"currentMode == %@",[NSRunLoop currentRunLoop].currentMode);
    }];

二、默认不会执行 ，需要添加到 当前RunLoop  可以指定具体的运行模式.NSRunLoopCommonModes 不是真正的模式，是占位模式（NSDefaultRunLoopMode、UITrackingRunLoopMode）都会执行。

NSTimer * timer = [NSTimer timerWithTimeInterval:2 repeats:YES block:^(NSTimer * _Nonnull timer) {
       NSLog(@"currentMode= %@",[NSRunLoop currentRunLoop].currentMode);
    }];
    
    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

NSTimer 会对target 产生强引用，如果target又对它们产生强引用，那么就会引发循环引用

1、使用block

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    //Block;
    __weak typeof(self) weakSelf = self;
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
        [weakSelf clickTest];
    }];
}

-(void)clickTest{
    NSLog(@"%@",[NSThread currentThread]);
}

- (void)dealloc
{
    [self.timer invalidate];
    NSLog(@"%s",__func__);
}

2、target: 使用代理对象   :target 必须为弱指针

方式一、继承NSObject

// YMProxy 类 
@interface YMProxy : NSObject
+(instancetype)proxyWith:(id)target;
//弱指针
@property (nonatomic,weak) id target;
@end
@implementation YMProxy
+(instancetype)proxyWith:(id)target{
    YMProxy * proxy = [[YMProxy alloc]init];
    proxy.target = target;
    return proxy;
}
//消息转发
-(id)forwardingTargetForSelector:(SEL)aSelector
{
    return self.target;
}
@end

//使用
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:[JMProxy proxyWith:self] selector:@selector(clickTest) userInfo:nil repeats:YES];
}

-(void)clickTest{
    
    NSLog(@"%@",[NSThread currentThread]);
}

- (void)dealloc
{
    [self.timer invalidate];
    NSLog(@"%s",__func__);
}

方式二、继承NSProxy

//JMProxy
@interface JMProxy : NSProxy
+(instancetype)proxyWith:(id)target;
//弱指针
@property (nonatomic,weak) id target;
@end
@implementation JMProxy
+(instancetype)proxyWith:(id)target
{
    JMProxy * proxy = [JMProxy alloc];
    proxy.target = target;
    return proxy;
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel
{
    return [self.target methodSignatureForSelector:sel];
}
-(void)forwardInvocation:(NSInvocation *)invocation
{
    [invocation invokeWithTarget:self.target];
}

//使用
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:[JMProxy proxyWith:self] selector:@selector(clickTest) userInfo:nil repeats:YES];
}

-(void)clickTest{
    
    NSLog(@"%@",[NSThread currentThread]);
}

- (void)dealloc
{
    [self.timer invalidate];
    NSLog(@"%s",__func__);
}