> On Jan 22, 2016, at 06:14, Dave <[email protected]> wrote: > > >> On 21 Jan 2016, at 23:40, Quincey Morris >> <[email protected]> wrote: >> >> On Jan 21, 2016, at 15:22 , Dave <[email protected] >> <mailto:[email protected]>> wrote: >>> >>> I’m relying of the copy attribute for the NSString’s, do I need to change >>> these to do a [xxxxxxx copy] too >> >> If you’re writing the setter yourself, you must do the copy yourself. If >> you’re using the synthesized setter, it’s done for you. >> >> In your own code, you may as well be liberal with ‘copy’. It’s basically >> free (in run-time cost) in situations where you don’t need it. You don’t >> save anything by leaving it out. >> > > I’ve always been confused over what *actually* happens when you do something > like this: > > @property (copy) NSString* pString; > > > self.pString = [anotherString copy]; > > Do two new NSString objects get created? (I mean using the synthesized setter)
The -copy method is called twice, but what that means in practical terms depends on the object being copied. If you're talking about NSString specifically, zero copies get created, as -copy on immutable foundation types is equivalent to -retain (or is a no-op under ARC). If "anotherString" is an NSMutableString, then one copy will be created by the explicit call to -copy in your example. But that copy will, itself, be an immutable NSString, so the second copy will be a no-op. And, of course, if we were talking about some other class that doesn't have a similar optimization, two copies will be created. Regardless of the circumstances, that explicit copy is redundant (but harmless) under ARC, and will cause a memory leak under MRR. _______________________________________________ Cocoa-dev mailing list ([email protected]) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [email protected]
