如果在队列中运行块，则内存使用量会增加

Question

I create a queue

dispatch_queue_t serialq = dispatch_queue_create("com.osletek.hill-billy", DISPATCH_QUEUE_SERIAL);

and put my blocks in it in a timer event, my memory usage keeps going up:

-(void) onTimer
{
 __weak typeof(self) this = self;
 dispatch_async(serialq, ^{
  UIImage *img = [this screenShot];
  // do something with img ...
 });
}
}

Without the queue, it works fine:

-(void) onTimer
{
 __weak typeof(self) this = self;

  UIImage *img = [this screenShot];
  // do something with img ...

}
}

I am using ARC.

Looks like the img object is not getting released if its in the queue.

How can I fix this mess?

Answer 1

There is no defined autorelease pool when running in a queue. There is when a timer fires.

Thus, change your code to this:

__weak typeof(self) this = self;
   dispatch_async(serialq, ^{
      @autorelease {
          UIImage *img = [this screenShot];
          // do something with img ...
      }
    });
}

UIImage should not cause issues when used from the non-main thread and the documentation explicitly states this. If that still shows memory accretion, I'd suggest you use the Allocations instrument to find out what and why.