How do i resolve EXC_BAD_ACCESS errors encountered

Question

I'm trying to do a simple thing; read an image from the internet, save it to the app's documents directory on the iphone, and read it back from that file so that i can do other things with it later. Writing the file works fine but when i try to read it back i get an EXC_BAD_ACCESS error in GDB that i have no idea how to resolve. Here is what my code basically looks like:

-(UIImage *) downloadImageToFile {
NSURL * url = [[NSURL alloc] initWithString: self.urlField.text];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

NSString *documentsDirectory = [paths objectAtIndex:0];

[paths release]
NSString * path = [documentsDirectory stringByAppendingString:@"/testimg.png"];

NSData * data = [[NSData alloc] initWithContentsOfURL:url];

[data writeToFile:path atomically:YES];

return [[UIImage alloc] initWithContentsOfFile:path];
}

The code fails in the return statement when i try to initialize the UIImage from the file. Any ideas?

Edit: neglected to add a release that was the problem in the code originally.

Answer 1

Definitely give memory management rules a quick review. Nothing jumps out that would cause the error you're getting, but you're leaking all those objects your allocating. If you don't understand the retain/release pattern, chances are there's another spot in your code where you're not retaining an object properly, and that's whats causing the EXC_BAD_ACCESS error.

Also note that NSString has methods for dealing with filesystem paths, you should never have to worry about the separator yourself.

Answer 2

These errors occur when you are mismanaging memory (ie. an object is being released prematurely or similar)

Try doing something like the following..

UIImage *myImage = [[UIImage alloc] initWithContentsOfFile:path];
return [myImage autorelease];

I spent a lot of time experimenting whilst getting to grips with the concepts of release/autorelease. Sometimes the retain keyword needs to be played also (although probably not in this case)

Another option could be simply the path does not exist, or cannot be read from?