On Apr 18, 2016, at 8:56 PM, Carl Hoefs <newsli...@autonomy.caltech.edu> wrote: > > Suppose I have an object with a declared method signature: > -(void)myMethod:(BOOL)a_bool; > > Q1: If I invoke it like this: > [self performSelector:@selector(myMethod:) withObject:nil]; // nil obj > Will argument a_bool end up with a 0 value assigned to it?
Probably, but it's poor practice to rely on it. The caller will store a pointer to either an argument-passing register or on the stack, depending on the platform. The called method will interpret only 1 of those 8 or 4 bytes, but, since they're all zero, it will get zero no matter what. > Q2: But if I invoke it like this: > [self performSelector:@selector(myMethod:) withObject:someObj]; // valid obj > Will argument a_bool end up with a 1 value assigned to it? No. The called method will interpret 1 of the bytes as a bool and that byte may be zero or non-zero, depending on the exact value of the non-nil object pointer that was passed. Since a valid object pointer may have a zero in, say, its least-significant byte, a_bool may be zero. You should use another mechanism for invoking the method or create a separate method which takes an object pointer and calls -myMethod: appropriately by interpreting that object pointer, and invoke that using -performSelector:…. 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
