Mac Forum / Programming / Mac Programming / August 2005

I asked about this a few days ago, and I thought the general answer was
that if I get an object as the return  value of a function, it has already
been autoreleased and I don't have to release it myself.  However, the
following code (which is from an email I posted earlier today on a
different topic), is taken from the docs and shows a returned object being
released when I am done with it:

int dropMethod = 0;
CFStringRef dropMethodKey = CFSTR("dropMethod");
CFNumberRef dropMethodVal = CFPreferencesCopyAppValue(dropMethodKey,
kCFPreferencesCurrentApplication);
if (dropMethodVal)
{
        if (!CFNumberGetValue(dropMethodVal, kCFNumberIntType,
&dropMethod))
                dropMethod = 0;
        CFRelease(dropMethodVal);
}
else dropMethod = 0;

So, how do I know if an object that has been returned from a function call
(message, whatever it's called) needs to be released when I'm
done using it?  In some cases, if I release the returned object of a
function, I get a warning suggesting I shouldn't be releasing it, but in
other cases, as shown above, a similar situation requires releasing such
an object.

I'm not detecting the pattern here.

Thanks.

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Keith Wiley         kwiley@cs.unm.edu         http://www.unm.edu/~keithw

"Yet mark his perfect self-contentment, and hence learn his lesson,
that to be self-contented is to be vile and ignorant, and that to
aspire is better than to be blindly and impotently happy."
                                           --  Edwin A. Abbott, Flatland
________________________________________________________________________