On May 29, 2014, at 2:52 PM, Trygve Inda wrote: > I have an array of objects. One property of this object is a ratio stored as > a string (e.g. 5:8, 9:4, 21:2) etc. > > I have a category on NSString: > > -(NSComparisonResult)compareAspectString:(NSString *)aString > > This does the division and compares the aspect ratios correctly. > > Now I need a predicate to do this. > > My Predicate says: > > Printing description of predicate: > aspectRatio >[cd] "4:3" > > But it is just doing straight string comparison. How can I get the predicate > to use by comparison method?
You can do this, but not using a predicate format string. One approach would be to use +[NSComparisonPredicate predicateWithLeftExpression:rightExpression:customSelector:]. The selector there, though, isn't a comparator. It returns TRUE if the comparison "passes"; FALSE otherwise. For example, you would be implementing a "greater-than-ratio" comparison, so the custom selector when sent to one value and passed another value would return TRUE if and only if the first value (the receiver) is greater than (as a ratio) the second value (the argument). Another approach would be +[NSPredicate predicateWithBlock:]. Regards, Ken _______________________________________________ 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
