What are the differences between Xcode generated .nib/.xib and interface builder .nib/.xib template?

Question

I am new to iPhone development so I have been working through some tutorials. What I don't understand is how xib fit into the work flow.

In a tutorial, one of the instruction is to create a new UIViewController subclass with "XIB for User Interface" selected. On my first try, I neglected to check that option and I thought may be I can just create the xib in Interface Builder but that didn't work. ( I created the xib using Cocoa Touch View Template, with the same name as the UIViewController and saved it the into project directory so it was added to the project.) I even changed the Class Identify for the File's Owner and hooked up the view outlet (the two differences I noticed when I inspected the xib generated from Xcode.)

So what are the differences between Xcode generated .xib (from UIViewController Template) and the IB .xib template?

Answer 1

XIB files created as part of the New File flow in Xcode have their File's Owner class pre-set, as well as certain outlets (view) already connected. Otherwise, there's not much difference.

Answer 2

The XIB File is basicly an uncompile NIB File, XIBs can always be edited in Xcode (unless they are outdated or corrupt) but most NIBs are compressed (flat) and are unopenable. However the older NIBs are bundles containing some source/archived including designable.nib which is often just the renamed XIB File and a keyedobjects.nib which is an other compiled NIB

---

NIB = Nxt Interface Builder

XIB = Xml Interface Builder

---

Although the new archived NIB files are unopenable to most applications including Xcode, they can still potentially be unarchived. I found this freeware application called NibUnlocker On The CharlesSoft Website which can potentially disassemble a compressed Nib file and exports it as an XIB document. This application is still fairly buggy but it is sometimes very accurate based on the Nibs contents.

(NibUnlocker is a very inaccurate name, Nibs are not locked they are archived)

---

Click to Download Nib Unlocker

---

If You wish to know a bit more you can read some additional information I have provided below in regards to the NIB and XIB Formats:

Nxt Interface Builder Anatomy:

Archived NIBs

A Compressed NIB file is complicated file to analyse but this is not impossible. The structure of these files are based off of a compacted property list (begins with "bplist00") and some of its contents are archived through NSKeyedArchiver. Since a NIB is formatted as a property list, This allows a small hack: if you actually change the extension of a Nib to .plist, eg. ArchivedNib.nib to ArchivedNib.plist You will actually be able to open it in Xcode viewing it as a Property List. When you view a Nib as a property list you will probably get a few base properties such as $version, $objects, $archiver and $top.

Useful Notes

A CFKeyedArchiverUID object is actually a redirector, in the {value = xx}, the value is an offset for a item in the $objects array from the start of the array. eg. <CFKeyedArchiverUID 0x60800002bc20 [0x7fffef6b8c30]>{value = 29}, value = 29, the result would be the 29th item in the $object's array. In Objective C you can retrieve this value from an NSArray with this method :

+ (NSUInteger)valueForKeyedArchiverUID:(id)keyedArchiverUID {
  void *uid = (__bridge void*)keyedArchiverUID;
  NSUInteger *valuePtr = uid+16;
  return *valuePtr;}

like if this helped ;-)

Answer 3

I'm not sure I'm following your question. When you created a xib file in Xcode, attempting to edit the xib file will bring up IB. So effectively you are using IB to edit the xib file in Xcode. I never tried creating a "stand-alone" xib file in IB and then hook it up to a project in xcode.

The only reason such an approach may not work is that when you create the xib file within the context of a project, there are associations created (such as "mainnib file base name" attribute in the plist) which will not be automatically generated when you attempt to use a standalone xib file with the xcode project.

Answer 4

It sounds like you configured the view xib properly, by setting the View outlet and configuring the custom class for File's Owner, but perhaps the problem was with the UIViewController subclass.

If your view controller subclass had implemented the -[UIViewController loadView] method directly, it'd prevent the NIB from loading. In the default implementation, the UIViewController will load the NIB file with the same name as the view controller. If you override this method to initialize the view a different way (e.g. completely programmatically), the default implementation that loads the NIB won't run.

Deleting an override of the -[UIViewController loadView] method in your subclass, or ensuring the names match, might resolve any discrepancies.

Answer 5

XIBs are XML. Diff them and find out for yourself.