Question

If I have this code

 NSString *postData = [@"foo=" stringByAppendingString:fooText.text];
 ...
 NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
 ...
 [postData release];   //this causes crash
 [request release];    //this causes crash

Now I understand this is the expected behavior according to Apple’s documents. Now if i remove the release code the crash doesn’t happen but I find that the memory leaks anyway for *request. So I rewrite the code

NSString *postData;
//postData = [NSString alloc];  // this line commented out since OP
postData = [@"foo=" stringByAppendingString:fooText.text];
...
NSMutableURLRequest *request;
request = [NSMutableURLRequest alloc];
request = [request initWithURL:url];
    ...
    [postData release];   //this still crashes #
    [request release];    //this works fine

I don’t really understand why it would crash at # . Is there any recommended best practice here? I think I must be missing something because I often see the ‘shorthand’ approach (top) having a release (Kochan, Programming in Objective-C for example), but the Apple docs say that it’s wrong.

Answer 1

The general rule of thumb, if you are calling a helper static method (such as stringByAppendingString), then you shouldn’t release it. That string was added to an autorelease pool before being given to you. If you are calling alloc then an init... method, then you are responsible for releasing that object.

Other things to note in your code:

• In the second example, you alloc postData, then immediately replace it with another string created by stringByAppendingString, that is a memory leak.
• Your release calls are wrong, they should be [postData release] and [request release]
• I don’t see any correlation between postData and request in your example, so not sure exactly what you are getting at with the two of them.