Question

I’m currently teaching myself Objective-C and Iphone Development using the very good ‘Begining IPhone Development’. I have been playing around with one of the sample applications and I am trying to update one button with text from a text field when another button is pressed. I have set up my Actions and links and all that jazz. The code of the single method/function/call is below

-(IBAction)updateButtonPressed
{
NSString *newCaption = [[NSString alloc] initWithString:@"."];

newCaption = tfUpdateText.text;
[btnPressMe setTitle:newCaption forState:UIControlStateNormal];

[newCaption release];


}  

It works perfectly the first time I press the button and maybe for two or three times after then crashes. I’m obviously doing something really stupid but I cant see it. This is all I added (as well as declarations, property – synthesize etc). Can someone point out my obvious memory leak.

Update:

If I change to this

-(IBAction)updateButtonPressed
{

[btnPressMe setTitle:tfUpdateText.text forState:UIControlStateNormal];



}  

It works fine but could someone explain to me what mistake I was making?

Answer 1

You are incorrectly managing memory. What is the -initWithString:@"." for? You’re generating a constant string @”.”, then leaking it, then pointing to a different string (tfUpdateText.text), then assigning that pointer to the title, then releasing the -text object.

This is both a leak and an over-release. It’s the over-release that’s crashing.

Perhaps you meant this:

-(IBAction)updateButtonPressed
{
    [btnPressMe setTitle:tfUpdateText.text forState:UIControlStateNormal];
}