awakeFromNib and applicationDidFinishLaunching

awakeFromNib is called on every object that is initialized or referenced from within a nib file.

In this nib file, I have references to two pieces of custom code: The Window Controller and the Window itself. So which of these two gets the awakeFromNib call? Both do.

Specifically, when a nib file has completed initializing all of the objects, it then loops back through every object referenced in the nib and if the object responds to awakeFromNib, it calls awakeFromNib on the object. Therefore, you can have logic in any or all of your objects in the awakeFromNib call.

Call order

In the second example above, it is possible to have an awakeFromNib method and an applicationDidFinishLaunching: method in the AppDelegate. Which would be called first and why?

The answer is that the awakeFromNib will be called first. When the nib file has been initialized, each object referenced in the nib will be looped through and they will all receive an awakeFromNib call if they respond to the message. After all of that is done then the Application’s delegate will receive the applicationDidFinishLaunching: call. This is the notice that everything is loaded and that the application is ready to start receiving user input.

Conclusion

If your code is localized to only the object you are working with then putting the code in the awakeFromNib is the perfect place for it. However, if your code is going to be manipulating more than one object in the nib then it is probably safer to put it in the applicationDidFinishLaunching: instead. This will insure that everything is loaded, referenced and ready to go.