Question

I have a UITableViewController subclass that’s instantiated, depending on where it’s used, in a NIB or via code. In both cases I want to do customization in the initializer method. Does that mean I need to implement both initWithNibName:bundle: and initWithCoder:, and would each method call its respective super initializer?

While I don’t need this right now, what if I also want to be able to instantiate the view controller with initWithStyle:? Would I then need 3 different init methods that replicate the same behavior?

It seems like this violates the whole designated initializer convention, as there would essentially be 3 separate initializers that don’t end up calling a common init method. Or is there a way to create a common designated initializer while supporting the 3 different instantiate routes?

Answer 1

My confusion was based on the mistaken belief that each class should have a single designated initializer. This is not true, and in the case of UITableViewController there are 3 designated initializers (as far as I can tell):

1. initWithStyle: declared locally
2. initWithNibName:bundle: inherited from UIViewController
3. initWithCoder: from adopting NSCoding protocol

You need to override 1 or more of these in your subclass depending on how your subclass gets instantiated. In my case I had to implement #2 and #3 since the class can be loaded from a NIB, or instantiated via code with reference to a NIB. (I imagine it’s rare that you’ll use both initWithStyle: and initWithNibName:bundle: for a single class.)

I found Apple’s Coding Guidelines for Cocoa helpful.