release array created from parameter

Question

How can I release an array created from a parameter?

I have function like

-(NSMutableArray*)composePhrase:(NSString*) phraseLiteral{
   ...
   NSArray* wordLiterals=[phraseLiteral componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"[]"]];
   ...
   [wordLiterals release];
}

and I always got problem with this release. Can anyone tell me how to make it right?

Answer 1

You need to understand the Object Ownership Policy.

You only gain the ownership automatically when the method name contains alloc, new or copy. Here, componentsSperatedByCharactersInSet: does not. Therefore, the returned wordLiterals is not owned by you. It's autoreleased. You shouldn't release it. It's released automatically when the autorelease pool is drained when the current event loop is complete.

If you want to keep the object, you retain it. Then you own it. When you no longer needs it, you release it.

Answer 2

The array returned by componentsSeparatedByCharactersInSet:... is autoreleased. This is true of pretty much all objects created like this -- ie, not via alloc or copy.

You are expected to retain it yourself if you want to keep hold of it. Otherwise it will evaporate at some unspecified future time (or if it doesn't it's not your responsibility).

Calling release on something you don't own will inevitably lead to grief down the line, so don't do it. In this case, since you seem to be using it only within the same scope, you can just let it take care of itself.