fast-enumeration

I am trying to fast enumerate through all of my collection view cells, however this implementation below is giving me a warning. for cell in self.collectionView?.visibleCells() as [UICollectionViewCell] { // Do Stuff } Error below appears on first line: Operand of postfix '?' should have optional type; type is '(UICollectionView, cellForItemAtIndexPath: NSIndexPath) -> UICollectionViewCell' I've tried messing around with optionals and had this working in Xcode 6 Beta 6, but to no avail in "Beta 7" How do i get rid of this error? / Write a loop that goes through all my CollectionView Cells ?

It seems from experimentation that the collection expression is evaluated only once. Consider this example: static NSArray *a; - (NSArray *)fcn { if (a == nil) a = [NSArray arrayWithObjects:@"one", @"two", @"three", nil]; NSLog(@"called"); return a; } ... for (NSString *s in [self fcn]) NSLog(@"%@", s); The output is: 2010-10-07 07:37:31.419 WidePhotoViewer Lite[23694:207] called 2010-10-07 07:37:31.420 WidePhotoViewer Lite[23694:207] one 2010-10-07 07:37:31.425 WidePhotoViewer Lite[23694:207] two 2010-10-07 07:37:31.425 WidePhotoViewer Lite[23694:207] three indicating that [self fcn] is

This question already has an answer here: Fast Enumeration on NSArray of Different Types 5 answers I am running a for-in loop over an NSMutableArray . There are instances of Class A in the array also out of those some are actually instances of its subclass B . So If I only want members of subclass B , I am checking the class of each object I get in an if condition inside the loop body. Is it possible that instead of writing something like this, for(A* obj in collection){ if([obj isKindOfClass:[B class]]){ //take some action. } } I can do something like this? for(B* obj in collection){ //take

I thought that I knew how to use fast enumeration, but there is something I don't understand about it. If I create three NSString objects and three NSNumber objects and put them in an NSMutableArray : NSString *str1 = @"str1"; NSString *str2 = @"str2"; NSString *str3 = @"str3"; NSNumber *nb1 = [NSNumber numberWithInt:1]; NSNumber *nb2 = [NSNumber numberWithInt:2]; NSNumber *nb3 = [NSNumber numberWithInt:3]; NSArray *array = [[NSArray alloc] initWithObjects:str1, str2, str3, nb1, nb2, nb3, nil]; then I make do fast enumeration on all NSString objects, like this: for (NSString *str in array) {