Duplicate Symbols for Architecture arm64

Question

When I try running my Xcode Project it fails with an error stating that I have duplicate symbols. I looked online where the find these duplicates but have had no luck:

Answer 1

If you are moving to Xcode 7 or 8 and are opening a really old project, I've encountered this problem:

in SomeConstFile.h

NSString * const kAConstant;

in SomeConstFile.m

NSString *const kAConstant = @"a constant";

Earlier versions of the compiler assumed that the definition in the header file was extern and so including SomeConstFile.h all over the place was fine.

Now you need to explicitly declare these consts as extern:

in SomeConstFile.h

extern NSString * const kAConstant;