iOS Odd looking code

[larswik]

I was on the App Developers forum figuring out what I need to fill out to send in my first app and I saw someone was having problems with code crashing. In his post I saw this code

-(void)drawRect:(CGRect)rect
{
    UIImage *navImage = [UIImage imageNamed: @"top bar image.png"];
    [navImage drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
    [navImage release];
    [self release];
}

Right off the bat I knew [Self release]; is bad. But as I looked at it I saw that he created a method with no return, fine. Next he creates a UIImage object and assigns a png to it. Next step he makes a Rect for the image but then after all that it looks like he releases his navImage without doing anything with it, like add to subview, Dictionary or something.

Am I wrong in understanding it?

 

[jnoxx]

He is creating an image pointer which uses a convencience method, so this will crash, because his pointer will be auto-released. And will therefore crash when you try to release again. (release sent to deallocated instance). hope that helps.

PS: he is not creating a rect just for nothing, his method is DRAWinrect, means he will draw the image inside the rect, otherwise it'd just be initWithFrame, or CGRectMake, or whatever.

 

[larswik]

Thank you for the clarification. I have not explored DrawInRect yet. I knew Self Release looked strange but then I thought he was releasing before doing anything. I see what is happening now with drawInRect

Thanks!