xcode 4.6.1 and LLVM 4.2: ld: 2 duplicate symbols for architecture armv7 - objective-c

Question

My first attempt at building a company iOS library/framework was this week, by following the steps found at this blog post here.
For reasons beyond this question, I can only link when building for a Device and not for simulator.
However, now I am getting a very bizarre error:
ld: 2 duplicate symbols for architecture armv7 clang: error: linker
command failed with exit code 1 (use -v to see invocation)
The lines in question suggest:
duplicate symbol _OBJC_CLASS_$_iContactsGridCell in:
/Users/*/Desktop/Projects/contactservice/branch/ContactServicesClient/DerivedData/iContacts/Build/Intermediates/iContacts.build/Debug-iphoneos/iContacts-5.1.build/Objects-normal/armv7/iContactsGridCell.o
/Applications/Xcode.app/Contents/Developer/Library/Frameworks/athium-iOS.framework/athium-iOS
duplicate symbol _OBJC_METACLASS_$_iContactsGridCell in:
/Users/*/Desktop/Projects/contactservice/branch/ContactServicesClient/DerivedData/iContacts/Build/Intermediates/iContacts.build/Debug-iphoneos/iContacts-5.1.build/Objects-normal/armv7/iContactsGridCell.o
/Applications/Xcode.app/Contents/Developer/Library/Frameworks/athium-iOS.framework/athium-iOS
Obviously the Class in question is iContactsGridCell.h
The class itself inherits from Cell.h
#interface iContactsGridCell : Cell
The class Cell.h is part of the framework, if I do not import the correct file, then as expected I get a semantic error: Cannot find interface declaration for Cell etc etc.
However, when I do import it, I get the following duplicate error.
This file is not included anywhere else in the project, apart from iContactsGridCell.h!
The file Cell.h in turn, is just a class found under the framework:
#interface Cell : NSObject
#property (strong,nonatomic) UIView *view;
#property CGRect rect;
#property int UID;
#property BOOL highlighted;
#property UIColor *b_colr;
- (id) initWithRect:(CGRect)frame;
- (BOOL) hasCoordinates:(CGPoint)coord;
- (void) ripple;
- (void) cubefy;
- (void) flipfy;
- (void) rotate;
- (void) setBg:(UIColor *)bg withAlpha:(CGFloat)alpha;
- (void) highlight;
- (void) unhighlight;
- (void) updateWithRect:(CGRect)rect;
#end
Why on earth am I getting the duplicate error?
What could be causing this?
How could it get fixed?
How can I get more info more verbose output of where the duplicates are found?
PS: I have followed the intructions found at the blog to the letter. Yet I cannot link for simulator (getting a wrong architecture error) so my guess that maybe something is broken in the framework and not the project itself. Could this be the reason for the duplicate errors?

Answer 1

There are several places where this error could be arising. I would do the following to start searching for the problem:
Search the project folder with finder and see if anywhere else the file "iContactsGridCell.h" exists. Or if any two files exist somewhere.
Make sure that you don't have two Objects that are of Class iContactsGridCell that share the same name for example:
iContactsGridCell *myObj;
iContactsGridCell *myObj;
Make sure your not doing anything like this: #import
"iContactsGridCell .m"
Or like this: #import "iContactsGridCell.h" #import "iContactsGridCell.h"
Make sure your not re-declaring a class (including ones that Apple has provided in their frameworks)
Main Point: That's all I can think of off the top of my head. But the thing to remember is that somewhere in your project resides two objects, class declarations etc. That are the same. And the compiler is complaining because of it.
Why the Compiler would complain (more info): While this information is really "unnecessary" it's good practice as a programmer to understand what's going on under the hood and will often help debug, so here's a little info on compilers:
Remember that a Compiler (while much more complex) is a program just like the ones that you create using it. One of the steps in most (if not all) compilers go through at one point or another reading code is creating "Symbols or Keys" for each variable, class, struct ect. So, at some point the compiler reached a line of code that "repeats / duplicates" somewhere else. So the "Key/Symbol" creation process done routine by the compiler fails.