这是我的问题：
我有有一个模型类NSTimer它，我希望定时器为模型对象的整个生命周期中运行。 Initiliazation很简单：我只是在下面一行代码init方法：
self.maintainConnectionTimer =
[NSTimer scheduledTimerWithTimeInterval:1
target:self
selector:@selector(maintainConnection)
userInfo:nil
repeats:YES];
不过，我的问题是， 我怎么否定这一计时器，当模型从内存中释放？ 现在，这通常会是容易的，但是，据我所知，则在计划NSTimer操作系统保持着强劲的指针Timer对象。
我应该如何处理呢？ 是否有一个模型从内存中释放之前的权利被调用的方法？
在[NSTimer scheduledTimerWithTimeInterval:...] 保留了目标 ，所以如果目标是自己 ，那么你的模型类的实例将永远不会被释放。
作为一种变通方法，可以使用一个单独的对象（称为TimerTarget在下面的示例中）。 TimerTarget有弱引用ModelClass ，以避免保留周期。
这种“辅助类”看起来是这样的。 它的唯一目的是计时器事件转发到“真正的目标”。
@interface TimerTarget : NSObject
@property(weak, nonatomic) id realTarget;
@end
@implementation TimerTarget
- (void)timerFired:(NSTimer*)theTimer
{
[self.realTarget performSelector:@selector(timerFired:) withObject:theTimer];
}
@end
现在，在你的模型类，你可以创建一个定时器和无效它dealloc ：
@interface ModelClass ()
@property(strong, nonatomic) NSTimer *timer;
@end
@implementation ModelClass
- (id)init
{
self = [super init];
if (self) {
TimerTarget *timerTarget = [[TimerTarget alloc] init];
timerTarget.realTarget = self;
self.timer = [NSTimer scheduledTimerWithTimeInterval:1
target:timerTarget
selector:@selector(timerFired:)
userInfo:nil repeats:YES];
}
return self;
}
- (void)dealloc
{
[self.timer invalidate]; // This releases the TimerTarget as well!
NSLog(@"ModelClass dealloc");
}
- (void)timerFired:(NSTimer*)theTimer
{
NSLog(@"Timer fired");
}
@end
因此，我们有
modelInstance ===> timer ===> timerTarget ---> modelInstance
(===> : strong reference, ---> : weak reference)
请注意，有来自计时器到模型类的实例没有（强）引用了。
我已用下面的代码，它创建的实例测试这ModelClass和5秒后释放它：
__block ModelClass *modelInstance = [[ModelClass alloc] init];
int64_t delayInSeconds = 5.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
modelInstance = nil;
});
输出：
2013-01-23 23:54:11.483 timertest[16576:c07] Timer fired
2013-01-23 23:54:12.483 timertest[16576:c07] Timer fired
2013-01-23 23:54:13.483 timertest[16576:c07] Timer fired
2013-01-23 23:54:14.483 timertest[16576:c07] Timer fired
2013-01-23 23:54:15.483 timertest[16576:c07] Timer fired
2013-01-23 23:54:15.484 timertest[16576:c07] ModelClass dealloc
基于@马丁 - [R想法，我创建使用哪个更容易，并添加一些检查，以避免崩溃的自定义类。
@interface EATimerTarget : NSObject
// Initialize with block to avoid missing call back
- (instancetype)initWithRealTarget:(id)realTarget timerBlock:(void(^)(NSTimer *))block;
// For NSTimer @selector() parameter
- (void)timerFired:(NSTimer *)timer;
@end
@interface EATimerTarget ()
@property (weak, nonatomic) id realTarget;
@property (nonatomic, copy) void (^timerBlock)(NSTimer *); // use 'copy' to avoid retain counting
@end
@implementation EATimerTarget
- (instancetype)initWithRealTarget:(id)realTarget timerBlock:(void (^)(NSTimer *))block {
self = [super init];
if (self) {
self.realTarget = realTarget;
self.timerBlock = block;
}
return self;
}
- (void)timerFired:(NSTimer *)timer {
// Avoid memory leak, timer still run while our real target is dealloc
if (self.realTarget) {
self.timerBlock(timer);
}
else {
[timer invalidate];
}
}
@end
这里是我的示例类
@interface MyClass
@property (nonatomic, strong) NSTimer *timer;
@end
@implementation MyClass
- (id)init
{
self = [super init];
if (self) {
// Using __weak for avoiding retain cycles
__weak typeof(self) wSelf = self;
EATimerTarget *timerTarget = [[EATimerTarget alloc] initWithRealTarget:self timerBlock: ^(NSTimer *timer) {
[wSelf onTimerTick:timer];
}];
self.timer = [NSTimer timerWithTimeInterval:1 target:timerTarget selector:@selector(timerFired:) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode];
}
return self;
}
- (void)dealloc
{
[self.timer invalidate]; // This releases the EATimerTarget as well!
NSLog(@"### MyClass dealloc");
}
- (void)onTimerTick:(NSTimer *)timer {
// DO YOUR STUFF!
NSLog(@"### TIMER TICK");
}
@end
