How to declare an NSString with multiple possible values - iphone

Question

I want to declare an NSString object to use within an alert, but its actual content depends on various factors, determined by some variable. I'm wondering how best to approach this. In most cases I've done something like this:
- (void)info {
NSString *targetString = [[NSString alloc] init];
switch (self.target) {
case 1:
targetString = #"ONE";
break;
case 2:
targetString = #"TWO";
break;
case 3:
targetString = #"THREE";
break;
default:
targetString = #"";
break;
}
NSString *message = [[NSString alloc] initWithFormat:#"Text: %#", targetString];
UIAlertView *alert = [[UIAlertView alloc]
initWithTitle:#"Info"
message:message
delegate:self
cancelButtonTitle:#"Ok!"
otherButtonTitles:nil];
alert.tag = kInfoAlert;
[alert show];
[alert release];
[targetString release];
[message release];
}
However when I run this through the build analyser, I get messages telling me the string is leaking memory:
First of all it says:
Value stored to 'targetString' during
its initialization is never read
Then:
Potential leak of an object allocated
on line 137 and stored into
'targetString'
These 2 comments are at line 136 and 137, where line 136 is
NSString *targetString = [[NSString alloc] init];
An alternative might be to declare the string as
NSString *targetString;
and set it in each case as
targetString = [NSString stringWithFormat:#"ONE"];
etc
Or even allocing the String in each case in order to release it at the end...
Well, what would be the best approach here?
Thanks,
Michael :)

Answer 1

The reason for your memory leak is because you are needlessly allocating a string with this line
NSString *targetString = [[NSString alloc] init];
and then setting it to a literal object. Define targetString as nil because when you set it to another value like targetString = #"ONE" you are no longer referencing the empty string you allocated and that causes a memory leak. As for your approach of the switch case for determining the value that is fine.

Answer 2

I believe this would be enough:
NSString *targetString = nil;
And you don't need to release targetString then.

Answer 3

How about this instead of the switch:
- (NSString*) stringForIndex: (NSUInteger) index
{
NSParameterAssert(index < 4);
id strings[] = {#"none", #"one", #"two", #"three"};
return strings[index];
}