Weird Memory Problem of Cocoa Application

I am writing a Cocoa program for Mac, and it includes a picture viewer. What the picture viewer's job is to download a picture from web and show it. It would do this every time I click a button who would give it a picture URL. So this would be frequent.

My design goal is, every time after I change to another picture or close it temporarily (it is not the main window), it will release the memory it takes. For example, before I open the picture viewer for a picture, my application takes 1M memory. After I open a picture, it takes about, say, 2M memory. And after I close it, it will decrease the memory usage to the original 1M.

The problem is, sometimes after I viewed a picture, especially a big one, the viewer won't give all the memory it took, for example, opening it cost about 20M memory, but after I close it, just 10 of the 20 released, the another 10 is still there and never be freed. It looks like memory leak, but I checked my code and analyzed it many times, I couldn't find any memory leak, and also, some other pictures won't behave like开发者_开发问答 this.

this is weird, is this possibly certain Cocoa internal memory cache policy? Any suggestions would be appreciated. Thanks in advance!

Update: Today after I added a scrollView as a wrapper of the imageView, this weird memory problem seems almost fixed.

Thanks for your advice, edc1591, I will continue to figure out what happened.

Without seeing the code it's hard to tell quite what the problem is. But until I see the code, I'll give you a few pointers for dealing with this:

• Enable Garbage Collection. If you already have it enabled, try forcing a garbage collection after releasing the image file like this:

  [[NSGarbageCollector defaultCollector] collectIfNeeded];

• Try heapshot analysis. Here's a good tutorial on that.

I'll update this answer once the code has been posted.