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Re: [OT] Retain count riddle

On Mar 30, 2004, at 1:49 PM, Sailesh Agrawal wrote:
#define SAFE_SET(old, new) [new retain]; [old release]; old = new;

...

- (void) foo : (NSString*)path {
SAFE_SET(m_Path, [path lastPathComponent]);
}

There are three style issues I'd bring up with this code.

First, I wouldn't use a setter macro. I'd actually write out (or have generated) the actual setter code. I find it's easier to maintain code that uses the actual code instead of macros.

Second, I wouldn't use MFC-style naming of instance variables. It doesn't play nicely with key-value coding. (Fortunately, I can at least commend you on not using Hungarian notation!)

Finally, you're doing work in a setter. That's the cause of the actual bug, but it's also a stylistic issue. I prefer to do as little work as possible in setters, and to make it clear what work is being done if it's anything other than (say) a -setNeedsDisplay: or (before bindings) a value-changed notification broadcast.

So if I were writing this, it'd look like:

// this is "foo" above
- (void)setPathToLastPathComponentOfPath:(NSString *)fullOrPartialPath
{
[self setPath:[fullOrPartialPath lastPathComponent]];
}

// this is the "path" setter
- (void)setPath:(NSString *)aPath
{
if (path != aPath) {
NSString *temp = [aPath copy];
[path release];
path = temp;
}
}

Yeah, it's a little more verbose, but I think the intent's clearer. And the path setter could be generated by a tool.

-- Chris

--
Chris Hanson <email@hidden>
http://www.livejournal.com/users/chanson/
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References: 
 >[OT] Retain count riddle (From: "Sailesh Agrawal" <email@hidden>)



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