Why must I hookup an IBOutlet twice in a custom NIB / XIB?

I have created a custom myViewController class and it has the default view, as well as an IBOutlet (topleftView) to a subview.

I have created a custom NIB/XIB file to load this myViewController.xib. Inside the XIB file I have set the file owner to myViewController and set the UIViewController identity class to myViewController as well.

My question is why do I have to hook up and draw a reference from the IBOutlet in the subview to both the file owner AND the UIViewController in interface builder?

Just trying to get my head around it since this is the first time I'm creating a custom NIB/XIB. I usually just did everythi开发者_如何学Cng in MainWindow but my application is getting too large so I want to spread things out.

If I don't have these multiple connections for the one IBOutlet to both the UIViewController and File Owner in the same nib file I crash with _EXC_BAD_ACCESS_ errors.

"Inside the XIB file I have set the file owner to myViewController ..."

I'm not sure what you are doing here. I think this is where the problem is. How many items do you have on the top level of your XIB? It should just be File's Owner, First Responser and a View. If there is another controller object in here, that's your problem. Get rid of it.

"...and set the UIViewController identity class to myViewController as well"

This part is correct. To connect your custom UIViewController to the XIB, clock on your "File's Owner", go to the "Identity Inspector" then look under "Class Identity" at the "Class" field. Set this to 'myViewController' (or whatever you named it).

At this point you should do 1 ctrl-drag from your File's Owner for each outlet you have setup.

My question is why do I have to hook up and draw a reference from the IBOutlet in the subview to both the file owner AND the UIViewController in interface builder?

Short answer: You don't. Just set your File's Owner's class to the class name of your UIViewController subclass and you're set.