Question

I work on a project on iPhone iOS with Xcode 4.

With Xcode > Product >Analyze I get 35 issues, all of this type:

 myTextField.text = [[NSString alloc] initWithFormat:@"0.2f", abc];

and the problem is “Potential leak of an object allocated at …”

What is the offending object and how can I release it?

Thanks

Answer 1

You’re leaking the string that you’re assigning to myTextField.text. When this assignment happens, a copy is being made (look at the property definition in the documentation). In most cases, when values are immutable, as is the case with NSStrings, a copy will give you an instance that points to the same location as the object that is being copied, with the retain count incremented by 1.

In the case of your code:

myTextField.text = [[NSString alloc] initWithFormat:@"0.2f", abc];

The retain count of the string that you’ve allocated is 2.

You will either need to (1) release, (or autorelease) the string, or (2) use one of the NSString convenience methods, e.g. stringWithFormat: to create the string. This will give you an autoreleased string so you won’t have to worry about explicitly releasing it.

(1)

NSString *str = [[NSString alloc] initWithFormat:@"0.2f", abc];
myTextField.text = str;
[str release]

or

myTextField.text = [[[NSString alloc] initWithFormat:@"0.2f", abc] autorelease];

(2)

myTextField.text = [NSString stringWithFormat:@"0.2f", abc]; // autoreleased