直接官方介紹看圖
image
將target強引用非春，引用計數(shù)+1，因此避免循環(huán)飲用的理論：
@property (weak ,nonatomic) NSTimer *timer;這樣寫不通的席怪。因為target引用計數(shù)已經(jīng)+1，target如果是ViewController纤控，頁面棧挂捻，pop出時，引用計數(shù)不會變成0船万，因此不會調(diào)用dealloc刻撒，ViewController依然在。
調(diào)用NSTimer方法中的invalidate耿导，可以將target引用計數(shù)-1声怔，由此可以解決內(nèi)存泄漏問題。
NSTime中Block官方介紹：
image
官方介紹：Block的方式可以避免循環(huán)引用
Block的方式舱呻，NSTimer不會將target引用計數(shù)+1醋火，因此，只關(guān)注Block循環(huán)引用問題即可。target會調(diào)用dealloc芥驳。
需要在dealloc中調(diào)用NSTimer的invalidate方法介粘，
如果不調(diào)用NSTimer的invalidate方法，NSTimer會一直執(zhí)行晚树，而target是nil姻采。具體原因和Runloop有關(guān)系，后續(xù)我們單獨再講Runloop和NSTimer的關(guān)系
調(diào)試代碼如下
@property (strong ,nonatomic) NSTimer *timer;
- (void)dealloc {
NSLog(@"Timer invalidate 前 = %ld",CFGetRetainCount((__bridge CFTypeRef)(self.timer)));
[self.timer invalidate];
NSLog(@"Timer invalidate 后 = %ld",CFGetRetainCount((__bridge CFTypeRef)(self.timer)));
NSLog(@"TestVC釋放了%@",self);
}
- (void)viewDidDisappear:(BOOL)animated{
[super viewDidDisappear:animated];
// [self.timer invalidate];
// NSLog(@"retainCount3 = %ld",CFGetRetainCount((__bridge CFTypeRef)(self)));
// self.timer = nil;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
// NSLog(@"retainCount0 = %ld",CFGetRetainCount((__bridge CFTypeRef)(self)));
[self creatTimer];
}
- (void)creatTimer {
[[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
// [self.timer fire];
}
- (NSTimer*)timer{
if(_timer==nil) {
__weak typeof(self) weakSelf = self;
// NSLog(@"retainCount1 = %ld",CFGetRetainCount((__bridge CFTypeRef)(self)));
// _timer = [NSTimer timerWithTimeInterval:1 target:weakSelf selector:@selector(timerForOverTimeOrder:) userInfo:weakSelf repeats:YES];
// NSLog(@"定時器前%@",weakSelf);
_timer = [NSTimer timerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {
// NSLog(@"fafafdfadfadxf%@",weakSelf);
NSLog(@"retainCount4 = %ld",CFGetRetainCount((__bridge CFTypeRef)(timer)));
// NSLog(@"fafafdfadfadxf%@",timer.userInfo);
// NSLog(@"dfafdada%@",self);
}];
NSLog(@"retainCount2 = %ld",CFGetRetainCount((__bridge CFTypeRef)(self.timer)));
}
return _timer;
}
- (void)timerForOverTimeOrder:(id)info {
NSLog(@"%@",info);
// NSLog(@"1111");
}
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