I'm stopped in my ( moderate) efforts to master XCode 4.3.2 by a trivial 
problem.
With anterior versions of Xcode + Interface Builder the creation of a 
class involved :
1) The creation of the *.h and *.m files
2) Instantiation in IB window of the new class Object by dragging it 
from the "Classes Library" of IB
Now, I'm certainly very dumb (or blind) because I'm unable to find this 
"Classes library" in XCode 4. Maybe the new class object is hiding 
somewhere ? At least  after creation of the class files it doesn't 
appear by itself in the <Objects> list of the project.
Thanks in advance for your help.

Xcode 4 changed things a lot with regard to Interface Builder.
Interface Builder won't create .h and .m files for you. You have to
create the class files yourself. Choose File > New > File to add a
class file to your project.

The Interface Builder Object item you use to instantiate your classes
is in Xcode 4's object library. Choose View > Utilities > Show Object
Library to show the object library, which appears in the lower right
corner of the project window. Type Object in the search field at the
bottom of the object library to find the Object item in the object
library.

Mark Szymczyk
Author, Xcode Tools Sensei
http://www.meandmark.com

On 16/05/12 05:39, Mark wrote:
> Xcode 4 changed things a lot with regard to Interface Builder.
> Interface Builder won't create .h and .m files for you. You have to
> create the class files yourself. Choose File>  New>  File to add a
> class file to your project.
>
> The Interface Builder Object item you use to instantiate your classes
> is in Xcode 4's object library. Choose View>  Utilities>  Show Object
> Library to show the object library, which appears in the lower right
> corner of the project window. Type Object in the search field at the
> bottom of the object library to find the Object item in the object
> library.
>
> Mark Szymczyk
> Author, Xcode Tools Sensei
> http://www.meandmark.com
Thank you, Mark, for your help.
If I summarize, The way to a new class in XCode 4 is the following :
1�)Create the .h and .m files , the same way as before ( from the top 
menu :File->New->File)
2�)Fish the blue cube "Object" from the Object Library and drag it to 
the <Objects> pane of XCode4 IB window
3�)Use the identity inspector to settle the class name. Either by 
picking it's name in the drop-down list, which , BTW, is the equivalent 
of the "good old" IB <Classes Library> tab, or by beginning to type it's 
name in the <class> textField( code completion works there)
Point 3 is essential because I found to my surprise that it is possible 
to override the name of "Object", by typing "myNewClass"directly in the 
list, and then make connections to other listed class instances !
Of course these phantom connections disappear at building and the App 
won't work, but I think users should be warned against that, waiting a 
correction of the interface.