选项卡式应用程序中用于视图控制器的其他NIB

Question

{Xcode 4.2, deployment target iOS4.3, not storyboard, using ARC}

I started with a tabbed application template & chose the universal platform, which nicely gives me view controller classes & NIB files for an iPhone ( ClassName_iPhone.xib ) & an iPad ( ClassName_iPad.xib ) for 2 tabs, with an if statement in the AppDelegate to determine which to run - exactly how I wanted it set up.

I wanted to add a 3rd & 4th tabs, so starting with the 3rd tab (doing 1 at a time) I created a new UIViewController subclass. As it doesn't give the option to create both NIBs at once, I selected "Targeted for iPad", & had intended to create the iPhone NIB manually. I added a "_iPad" suffix to the created NIB file, then I created a user interface view NIB file to which I added the "_iPhone" suffix. I then set up the code for the new view controller in the AppDelegate implementation file to include the 3rd view controller & tab, & I used the other view controller classes as a guide to set up the new class's code.

For the 3rd _iPhone NIB, I dragged a view object from the objects library onto the canvas, & set it up as per the other 2 _iPhone NIBs. But when I went to connect the outlets, there is no view outlet in the referencing outlets of the connections panel to connect with, which I thought there should be. At this point I suspected something was wrong.

I tried running it in the simulator, in iPad mode it works fine (all 3 tabs are clickable). But in iPhone mode clicking the 3rd tab crashes it with a "SIGABRT" on thread 1. It's obvious what I did didn't work. I don't see anything in the output window that gives me any clues.

Being a newbie to obj-c, so not being too sure of the problem, I would have thought that I either:

• have used the wrong user interface template (view)
• should have used a view controller object from the object library (not a view)
• or that I should have declared some outlets in my view controller class files.

But if I should have done either of the latter 2, then my question would be why does the iPad NIB work then, when it clearly has a view object in the NIB & no outlets declared in the class files (same with the other 2 view controllers for both devices)?

Does the UITabView class somehow have outlets pre-declared within it for the first 2 tabs? But that still doesn't explain why the _iPad NIB works.

As usual, any help & advice much appreciated, & if there's a link to an explanation somewhere that I've missed, please show me, because I'm happy to do the research.

If what I've done wrong here is not determinable, then I guess ultimately what I'm asking is a clue to how best to create the second NIB file for iPhone to mesh with the class created with iPad NIB.

Answer 1

Sorry to answer my own question but with further searching I found this answer that was the solution, although not quite the whole story. So I thought to put what I did in an asnwer so others can refer to it.

As Piotr Czapla explains in the linked answer, for some reason Xcode doesn't populate the connectionRecords data, as you can see by my first red arrow. Having a look at the view controller that works (where second red arrow is), that's what the data should look like. So the answer is to cut the data & paste it into the NIB file, or type it. You can do this in Xcode by right-clicking the NIB file in the project navigatior & then Open As > Source Code, which is what you see in my screenshots.

The bit I want to add to Piotr Czapla's explanation though is the destination reference pointed to by the second red arrow might not be correct for the NIB file you're pasting into (mine wasn't) & Xcode might not let you go back into IB mode. If so, you need to get the correct reference from the IBUIView class within your NIB file, as pointed to by the third red arrow. Once I copied that reference to my destination reference ref=, as shown by the fourth red arrow, all was ok & the problem was solved. I could then go back into IB mode (right click, Open As > Interface Builder - iOS) & the view works in the simulator.