Enumerate Using Block

enumerateObjectsUsingBlock: is often the best way of passing through the contents of a collection. Objective-C fast enumeration (for (... in ...)) uses it under the hood, so it is fast, and you also have the advantage of the index number (for arrays) whilst iterating.

What some people appear not to know is that you don’t have to use id as the object parameter for the enumeration block. You don’t have to call it obj either.

Instead of:

[myArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    UIView *view = obj;
    if (indexOfViewToShow != idx)
        view.hidden = YES;
}];

It is perfectly allowable, and much more readable, to do:

[myArray enumerateObjectsUsingBlock:^(UIView *view, NSUInteger idx, BOOL *stop) {
    if (indexOfViewToShow != idx)
        view.hidden = YES;
}];

Of course, you have to be sure that everything in the array is a UIView, but this warning also applies to the first example.

On a related note, a similar principle applies when coding IBAction methods, though this has become more obvious now you can create actions by control-dragging - sender doesn’t have to be an id, it can be whatever class the originating object is.