problem initializing a custom class (UIImageView may not respond to '-alloc')

Question

I have an issue for this line

ball* balle = [[ball alloc] initWithPNGFileName:ballPath andGame:game andCGRect:CGRectMake( 200, 100, 16, 16 )] ;

the issue is ' ball undeclared' with warning: 'UIImageView' may not respond to '-alloc' and warning: no '-initWithPNGFileName:andGame:andCGRect:' method found

Here's the method:

-(id) initWithPNGFileName:(NSString *) filename andGame: (Game*) game andCGRect: (CGRect) imagerect_ {  
    [super init];

    CGDataProviderRef provider;
    CFStringRef path;
    CFURLRef url;


    const char *filenameAsChar = [filename cStringUsingEncoding:[NSString defaultCStringEncoding]]; //CFStringCreateWithCString n'accepte pas de NSString

    path = CFStringCreateWithCString (NULL, filenameAsChar, kCFStringEncodingUTF8);
    url = CFURLCreateWithFileSystemPath (NULL, path, kCFURLPOSIXPathStyle, NO);
    CFRelease(path);
    provider = CGDataProviderCreateWithURL (url);
    CFRelease (url);
    image = CGImageCreateWithPNGDataProvider (provider, NULL, true, kCGRenderingIntentDefault);

    CGDataProviderRelease (provider);

    imageRect = imagerect_ ;

    [game addToDraw: self] ;
    [game addToTimer : self] ;

    return self ;

}


-(void) draw: (CGContextRef) gc
{
    CGContextDrawImage (gc, imageRect, image );
}

I don't understand why UIImageView can't be allocated and why I have no '-initWithPNGFileName:andGame:andCGRect:' method found

Thanks

Answer 1

From the code you provide it seems that you have an instance of UIImageView called ball. Are you sure your Class is called ball (Class names should begin with a capital letter, by the way) and it's .h - file is properly included?

Some background information: alloc is a class method, you don't send it to an instance - it's signature is something like + (id) alloc; (mind the plus here!) Basically, the warning says that you try to invoke the instance method alloc on your object, which would have the signature - (id) alloc; (mind the minus here!), if it existed (which is most probably not the case). Therefore, the compiler recognizes ball not as a class name, but as an instance of UIImageView, which - as the warning indicates - may not respond to - (id) alloc; . By default, the compiler assumes that unknown methods return an instance of id (and not of ball as you expected), this is why it warns you that it can't find a method called -initWithPNGFileName:andGame:andCGRect for this object.