Thanks for that information - that’s very helpful. It sounds from what you are saying as if there is nothing wrong with me redefining the *property* in the subclass (as read-write), but that it’s just the synthesis itself that is the problem? Assuming that is the case, I can easily(*) rectify that by writing explicit setters/getters, so I will do that.
(*) there are rather a lot of these properties in the actual original code, but it just involves a lot of typing! On 5 Jul 2016, at 16:12, Keary Suska <cocoa-...@esoteritech.com> wrote: > >> On Jul 5, 2016, at 5:36 AM, Jonathan Taylor <jonathan.tay...@glasgow.ac.uk> >> wrote: >> >> I have a problem with property synthesis in my code, which I hope somebody >> can advise on. I find I have to write different property synthesis code for >> 32- or 64-bit builds in order to avoid compiler errors. >> >> A minimal demonstration of the problem can be found below - build as part of >> a fresh project on Xcode 5 or 6, with ARC disabled. It surprises me that I >> have to write different synthesis code for 32- or 64-bit builds - and this >> then makes me worry that I am doing something more fundamentally wrong. Can >> anyone comment (or explain)? >> >> [I appreciate that this code may be old-fashioned in style - I am not even >> sure what is or is not the recommended style these days. It seems to work >> though - and, importantly, as far as I can tell the synthesized property >> myFlag on MutableSettings *does* map to the same backing variable, even on a >> 64-bit build where I am not able to specify the backing variable in the >> synthesis statement] > > 32 vs 64 is likely coincidental, and probably has more to do with compiler > differences. I.e., at that time, there were additional compiler “features” > for 64 bit vs 32 bit. So my thought is that what you are doing is wrong in > both cases, but you are simply getting different compiler errors. > > The essential issue I believe is that you cannot re-synthesize in a subclass. > You will have to specify the setter explicitly. The issue in the second > (64-bit) case is that when you specify @synthesize with an instance variable > you are specifying a *new* instance variable on that class, but the compiler > correctly warns you that that instance variable has already been defined in > the superclass and therefore cannot also be defined in the subclass. The 32 > bit compiler seems to be letting you get away with this error, but it could > have horrible unintended consequences. _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) 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 arch...@mail-archive.com
