Question

So i spent the last hour or so fighting with my code, and eventually discovered that the NSSet I was trying to use was empty. Once I switched from the first line of code to the second, everything worked great. I was just hoping someone could tell me what is wrong with the first line. It compiles just fine, but apparently doesn’t do what I’m hoping for.

NSSet *singleOperandOperations = [singleOperandOperations initWithObjects: @"cos", @"sin", @"sqrt", nil];

v.s.

NSSet *singleOperandOperations = [NSSet setWithObjects: @"cos", @"sin", @"sqrt", nil];

Thanks!

Answer 1

setWithObjects: is a so called convenience constructor, which in fact does an alloc and then an initWithObjects:. setWithObjects: is just a little less typing. Note that the returned id of such a convenience constructor is autorelease‘d, by convention.

So your first example should be:

NSSet *singleOperandOperations = [[NSSet alloc] initWithObjects: etc...];

And this can be replaced by:

NSSet *singleOperandOperations = [NSSet setWithObjects: etc...];