objective c - Local variable assign versus direct assign; properties and memory

Question

In objective-c I see a lot of sample code where the author assigns a local variable, assigns it to a property, then releases the local variable. Is there a practical reason for doing this? I've been just assigning directly to the property for the most part. Would that cause a memory leak in any way? I guess I'd like to know if there's any difference between this:

HomeScreenBtns *localHomeScreenBtns = [[HomeScreenBtns alloc] init];
self.homeScreenBtns = localHomeScreenBtns;
[localHomeScreenBtns release];

and this:

self.homeScreenBtns = [[HomeScreenBtns alloc] init];

Assuming that homeScreenBtns is a property like so:

@property (nonatomic, retain) HomeScreenBtns *homeScreenBtns;

I'm getting ready to submit my application to the app store so I'm in full optimize/QA mode.

Answer 1

Assuming:

@property (nonatomic,retain) HomeScreenBtns *homeScreenBtns;

1. HomeScreenBtns *localHomeScreenBtns = [[HomeScreenBtns alloc] init];
2. self.homeScreenBtns = localHomeScreenBtns;
3. [localHomeScreenBtns release];

Then (1) implies a retain. (2) implies a second retain because the property says so. (3) releases the retain in the local scope created by (1).

If you don't do (3), you'll leak eventually.

This is all documented in the memory management guide.