Question

I’m sorry to ask such a simple question, but it’s a specific question I’ve not been able to find an answer for.

I’m not a native objective-c programmer, so I apologise if I use any C# terms!

If I define an object in test.h

@interface test : something {
    NSString *_testString;
}

Then initialise it in test.m

-(id)init {
    _testString = [[NSString alloc] initWithString:@"hello"];
}

Then I understand that I would release it in dealloc, as every init should have a release

-(void)dealloc {
    [_testString release];
}

However, what I need clarification on is what happens if in init, I use one of the shortcut methods for object creation, do I still release it in dealloc? Doesn’t this break the “one release for one init” rule? e.g.

-(id)init {
    _testString = [NSString stringWithString:@"hello"];
}

Answer 1

If you set an attribute with an autorelease, the object in the attribute can die at anytime beyond the immediate scope. Convenience methods i.e. ones that start with a type: string, array, dictionary etc, return autoreleased objects. You only use autoreleased objects when you don’t care whether or not they survive beyond the present scope.

What you really need to do in this case is use accessors, either the synthesized or custom, to manage your retention automatically.

If you do:

@property(nonatomic, retain)  NSString *_testString; // .h
@synthesize _testString; //.m

then in code use the reference form:

self._testString = [NSString stringWithString:@"hello"];

… then the only place you have to release _testString is in dealloc. The compiler will create synthesized accessors which will automatically manage the properties memory for you.

By the way, you should not use underscores for names. Apple reserves underscore names for itself so you can get a naming collision.