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sending release to nil
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sending release to nil


  • Subject: sending release to nil
  • From: Ted Lowery <email@hidden>
  • Date: Wed, 15 Jan 2003 23:29:52 -0500

Hi all-

As an ex-C++ programmer (I say 'ex' because I am completely sold on the ease of development and features of objective-C, now if I can only find a paying job...), I am used to the limitation of not being able to free an object more than once. Early on, my code was littered with:

if (obj) delete obj;
obj = NULL;

Then, as I learned, I created a free pattern (idea courtesy of Mike and Phani):

#define kill(x) if (x) delete x; x = NULL;

then I could free an object as much as I wanted.

Anyhow, now that I am discovering the power of objective-C, I notice I can send nil a release message, and it really doesn't care. So my current pattern is:

if (obj) [obj release];
obj = nil;

but I can also drop the if part, and code works fine.

My question is (I know, you were wondering if I would ever get to it?):

There is a performance hit for using if, and I assume there is a performance hit for sending release to nil. I would surmise the if is faster than messaging all the way to nil, though obj-C may do something cool for me that mitigates. Of course, I could be dead wrong as well.

I'm too lazy to build a test case, so I thought I'd pose to this group.

Hang on, the question is coming, I promise...

What patterns do you use?

if?
multiple releases to nil?
does it make a measurable difference if I bracket the release and nil assignments?
something else I'm not thinking of?

Thanks for the help, everyone.

Cheers, Ted
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