ARC中从未调用过注解dealloc方法，调用底层viewcontroller dealloc

Question

当我的应用程序在我的自定义注释方法中开始崩溃时，我了解到我的内存存在问题。我确信管理地图的视图控制器 100% 应该已经从视图堆栈中弹出。

这里是注解的代码，TaxiArrivingAnnotation.h：

#import <Foundation/Foundation.h>
@import MapKit;

@interface TaxiArrivingAnnotation : NSObject<MKAnnotation>
@property (nonatomic) CLLocationCoordinate2D coordinate;
@property (nonatomic) int minutesToTaxiArrival;

-(void) startTimer;
@end

和TaxiArrivingAnnotation.m:

#import "TaxiArrivingAnnotation.h"

#define SECONDS_IN_A_MINUTE 60

@interface TaxiArrivingAnnotation ()
@property (nonatomic) NSTimer * timer;
@property (nonatomic) NSDate * timeOfArrival;
@property (nonatomic, weak) id token1;
@property (nonatomic, weak) id token2;
@end

@implementation TaxiArrivingAnnotation

- (id)init
{
    self = [super init];
    if (self) {
        __weak TaxiArrivingAnnotation * this = self;

        self.token1 = [[NSNotificationCenter defaultCenter] addObserverForName:UIApplicationDidBecomeActiveNotification object:nil queue:nil usingBlock:^(NSNotification *note)
        {
            NSLog(@"DID BECOME ACTIVE");
            NSTimeInterval secondsLeft = [this.timeOfArrival timeIntervalSinceNow];
            if (secondsLeft < 0) {
                self.minutesToTaxiArrival = 0;
                return;
            }

            this.minutesToTaxiArrival = secondsLeft / SECONDS_IN_A_MINUTE;

            [this startTimer];
        }];

        self.token2 = [[NSNotificationCenter defaultCenter] addObserverForName:UIApplicationWillResignActiveNotification object:nil queue:nil usingBlock:^(NSNotification *note)
       {
           NSLog(@"WILL RESIGN ACTIVE");
           [this.timer invalidate];
           this.timer = nil;
       }];

    }
    return self;
}


-(void) setMinutesToTaxiArrival:(int)newMinutes {
    self->_minutesToTaxiArrival = newMinutes;
    self->_timeOfArrival = [NSDate dateWithTimeIntervalSinceNow:SECONDS_IN_A_MINUTE * newMinutes];
    if (newMinutes < 0) {
        [self.timer invalidate];
    }
}

-(void) startTimer {
    self.timer = [NSTimer timerWithTimeInterval:SECONDS_IN_A_MINUTE target:self selector:@selector(aMinutedPassed) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode];
}

-(void) aMinutedPassed {
    self.minutesToTaxiArrival--;
}

-(void) dealloc {
   NSLog(@"DEALLOC");
    if (self.timer != nil && [self.timer isValid])
        [self.timer invalidate];
    [[NSNotificationCenter defaultCenter] removeObserver:self.token1];
    [[NSNotificationCenter defaultCenter] removeObserver:self.token2];
}
@end

我在viewDidAppear 上添加注释并在viewDidDisappear 上删除它。不仅删除它，而且nil-ing 引用。管理视图控制器dealloc被调用时，dealloc方法仍然没有被调用。

真正的问题是，由于注释已被释放，计时器和通知会触发并且应用程序崩溃。

Answer 1

您正尝试在dealloc 中invalidate 您的重复计时器。问题是计时器保持对target（您的注释）的强引用，这将阻止dealloc 被调用（因为它仅在没有更多强引用时被调用）。它类似于强引用循环（又名保留循环）。

当您的视图控制器被解除分配（或任何启动视图控制器解除的逻辑事件）时，您必须invalidate 计时器。而且由于计时器在到达dealloc 时会失效，因此显然可以从注解的dealloc 方法中删除invalidate 代码。