in Obj-C, how could I make a switch statement that will evaluate classes, rather than just numbers?

Question

in Obj-C a switch can only evaluate numbers. I'd like to be able to use it to compare classes of objects, something like this, for instance:

switch (currentSubViewController.class) 
{
     case UITableViewController.class :
          <do stuff>
          break;
     case UICollectionViewController.class :
          <do stuff>
          break;
}

Is there any way to achieve this? I'd really like to be able to use a switch because it makes it so easy to read for different cases, and I can add more cases at any point in the future. Any ideas?

Answer 1

As described in this forum post you would be better off applying the Liskov Substitution Principle and put the <do stuff> logic in the actual class, and then call a method shared by a superclass all these classes inherit (or a protocol in Obj-C if you're planning to have this logic shared across totally different classes).

This encapsulates all the logic in each implementation/sub-class without a higher level class needing to worry about every single possible implementation you might have. This improves maintainability and is more common in Object Oriented Programming as opposed to plain old procedural programming.

Answer 2

The switch statement only works with integer types. You need a big if-else block.

If you really want to force a switch statement then you could work out something using a fixed array of classes and base the switch off of the index position of the class you are checking. But for readability in the case statements, you would need to define a set of constants representing the index position of each class. That's a lot of work and code to maintain just to avoid and if-else block.