Changing the background image?

Question

If I associate a UIImageView that is being used for the background image in my view,
In the header file:
IBOutlet UIImageView *theBackground;
@property (nonatomic, copy) UIImageView *theBackground;
and @synthesize it, in the implementation file:
@synthesize theBackground;
that I ought to be able to dynamically change that image (for example, in viewDidLoad) with the following statement:
theBackground.image = [UIImage imageNamed:@"Default2.png"];
But all that happens if I try that is that the program starts up and crashes.
Default2.png is present.
Anybody have an idea what I am doing wrong?
Thanks,
doug

Answer 1

I think this is because UIImage does not conform to the NSCopying protocol
According to [The Objective-C 2.0 Programming Language|http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/A rticles/chapter5_section5.html], @property(copy) creates something like
if (property != newValue)
[property release];
property = [newValue copy];
(note that the implementation may not be exactly as shown).
So in your program, UIImage is being sent a copy message.
[NSObject Class Reference|http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSOb jectClass/Reference/Reference.html#//appleref/doc/uid/20000050-copy] wrote:
-(id)copy
*Return Value*
The object returned by the NSCopying protocol method copyWithZone:, where the zone is nil.
Discussion
This is a convenience method for classes that adopt the NSCopying protocol. _An exception is raised if there is no implementation for copyWithZone:_.
NSObject does not itself support the NSCopying protocol. Subclasses must support the protocol and implement the copyWithZone: method
Regards,
Thomas