Debugging NSoperation BAD ACCESS within graphics context
- by Joe
I tried everything to debug this one but I can't get to the bottom of it.
This code lives in a subclass of NSOperation which is processed from a queue:
(borders is an ivar NSArray containing 5 UIimage objects)
NSMutableArray *images = [[NSMutableArray alloc] init];
for (unsigned i = 0; i < 5; i++)
{
CGSize size = CGSizeMake(60, 60);
UIGraphicsBeginImageContext(size);
CGPoint thumbPoint = CGPointMake(6, 6);
[controller.image drawAtPoint:thumbPoint];
CGPoint borderPoint = CGPointMake(0, 0);
[[borders objectAtIndex:i] drawAtPoint:borderPoint];
[images addObject:UIGraphicsGetImageFromCurrentImageContext()];
UIGraphicsEndImageContext();
}
[images release];
The code works fine most of the time but when I push the iphone by access subviews and pressing lots of buttons on the UI I either get this exception which is trapped by the operation:
Exception Load view: *** -[NSCFArray insertObject:atIndex:]: attempt to insert nil
or I get this:
Program received signal: “EXC_BAD_ACCESS”.
The exception is caused because UIGraphicsGetImageFromCurrentImageContext() return nil.
I don't know how to debug the EXC_BAD_ACCESS but I'm guessing that this error (in fact both of these errors) is caused by low memory. The debugger stops at the line:
[controller.image drawAtPoint:thumbPoint];
As I mentioned I've trapped the exception so I can live with that but the EXC_BAD_ACCESS is more serious.
IF this is memory related how can I tell and is it possible to increase the memory available to NSOperation?
