如何解决NSTimer的循环引用问题

最新推荐文章于 2024-08-25 21:56:58 发布

原创最新推荐文章于 2024-08-25 21:56:58 发布 · 1k 阅读

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本文分享了四种解决计时器问题的方法：使用类方法、创建NSProxy子类、使用Block和GCD的timer替换，每种方法都有详细的代码实现。

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总结了四种解决方案，与君共享

1、使用类方法

@interface TimerTarget : NSObject

@property (nonatomic, assign) SEL selector;
@property (nonatomic, weak) NSTimer *timer;
@property (nonatomic, weak) id target;

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)timeInterval target:(id)target selector:(SEL)selector userInfo:(nullable id)userInfo repeats:(BOOL)repeats;

@end


#import "TimerTarget.h"

@implementation TimerTarget

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)timeInterval target:(id)target selector:(SEL)selector userInfo:(nullable id)userInfo repeats:(BOOL)repeats {
    TimerTarget *timerTarget = [[TimerTarget alloc] init];
    timerTarget.target = target;
    timerTarget.selector = selector;
    timerTarget.timer = [NSTimer scheduledTimerWithTimeInterval:timeInterval target:timerTarget selector:@selector(timerSelector:) userInfo:userInfo repeats:repeats];
    return timerTarget.timer;
}

- (void)timerSelector:(NSTimer *)timer {
    if (self.target && [self.target respondsToSelector:self.selector]) {
        [self.target performSelector:self.selector withObject:timer.userInfo];
    } else {
        [self.timer invalidate];
    }
}

- (void)dealloc {
    printf(__func__);
}

@end



@interface TimerController ()

@property (nonatomic, strong) NSTimer *timer;

@end

@implementation TimerController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor whiteColor];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake(20, 100, self.view.frame.size.width - 40, 40);
    button.backgroundColor = [UIColor greenColor];
    [button setTitle:@"倒计时" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
}

- (void)buttonAction {
    self.timer = [TimerTarget scheduledTimerWithTimeInterval:2 target:self selector:@selector(timeFire) userInfo:nil repeats:YES];
    [self.timer setFireDate:[NSDate distantPast]];
}

- (void)timeFire {
    NSLog(@"开始计时");
}

- (void)dealloc {
    [self.timer invalidate];
    printf(__func__);
}

2、创建一个NSProxy的子类

@interface TimerProxy : NSProxy

@property (nonatomic, weak) id weakTarget;

- (instancetype)initWithTarget:(id)target;
+ (instancetype)proxyWithTarget:(id)target;

@end

#import "TimerProxy.h"

@implementation TimerProxy

- (instancetype)initWithTarget:(id)target {
    _weakTarget = target;
    return self;
}

+ (instancetype)proxyWithTarget:(id)target {
    return [[self alloc] initWithTarget:target];
}

//返回方法的签名。
- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {
    return [self.weakTarget methodSignatureForSelector:sel];
}

- (void)forwardInvocation:(NSInvocation *)invocation {
    SEL sel = [invocation selector];
    if ([self.weakTarget respondsToSelector:sel]) {
        [invocation invokeWithTarget:self.weakTarget];
    }
}

- (BOOL)respondsToSelector:(SEL)aSelector {
    return [self.weakTarget respondsToSelector:aSelector];
}

@end

@interface TimerController ()

@property (nonatomic, strong) NSTimer *timer;

@end

@implementation TimerController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor whiteColor];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake(20, 100, self.view.frame.size.width - 40, 40);
    button.backgroundColor = [UIColor greenColor];
    [button setTitle:@"倒计时" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
}

- (void)buttonAction {
    self.timer = [NSTimer scheduledTimerWithTimeInterval:2 target:[TimerProxy proxyWithTarget:self] selector:@selector(timeFire) userInfo:nil repeats:YES];
    [self.timer setFireDate:[NSDate distantPast]];
}

- (void)timeFire {
    NSLog(@"开始计时");
}

- (void)dealloc {
    [self.timer invalidate];
    printf(__func__);
}

3、使用Block

@interface NSTimer (WeakTimer)

+ (NSTimer *)jf_scheduledTimerWithTimeInterval:(NSTimeInterval)interval
                                       repeats:(BOOL)repeats
                                         block:(void(^)(void))block;

@end


#import "NSTimer+WeakTimer.h"

@implementation NSTimer (WeakTimer)

+ (NSTimer *)jf_scheduledTimerWithTimeInterval:(NSTimeInterval)interval
                                       repeats:(BOOL)repeats
                                         block:(void(^)(void))block {
    return [self scheduledTimerWithTimeInterval:interval
                                         target:self
                                       selector:@selector(jf_blockInvoke:)
                                       userInfo:[block copy]
                                        repeats:repeats];
}

+ (void)jf_blockInvoke:(NSTimer *)timer {
    void (^block)(void) = timer.userInfo;
    if(block) {
        block();
    }
}

@end


//创建timer
__weak typeof(self) weakSelf = self;
self.timer = [NSTimer jf_scheduledTimerWithTimeInterval:2  repeats:YES block:^{
    [weakSelf timeFire];
}];

4、GCD的timer替换

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
self.aTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
dispatch_source_set_timer(_aTimer, dispatch_time(DISPATCH_TIME_NOW, 0), 2 * NSEC_PER_SEC, 0);
dispatch_source_set_event_handler(_aTimer, ^{
    NSLog(@"%@", [NSThread currentThread]);
    dispatch_async(dispatch_get_main_queue(), ^{
        NSLog(@"开始计时");
    });
});
//开启计时器
dispatch_resume(_aTimer);

//结束计时
//dispatch_source_cancel(_aTimer);

查看Demo