objective-cswiftarm7

Not allowing to use Constant defined in Objective C header file in swift class. Undefined symbols for architecture armv7

I created Objective C Header file. and added some properties in it.
i declared
static NSString* const kColor005C98 = @"005C98"; in Constants.h file

I defined this file in Bridging-Header file as #import "Constants.h" Now when i want to use this property kColor005C98 in some swift file it failed the build and i am getting

Undefined symbols for architecture armv7: "_kColor005C98", referenced from:

i don't know what else i need to do so i don't get this error? (i have used this property in other objective C file successfully and no issue in that case)

Solution

  • Update:

    As of Swift 2/Xcode 7 and later, a static constant definition like

    static NSString* const kColor005C98 = @"005C98"; // in Constants.h file

    is imported to Swift and can be used without problems.

    (Old answer for Swift 1.x) When the code

    static NSString* const kColor005C98 = @"005C98"; // in Constants.h file

    is processed by an Objective-C compiler, it is treated as two things combined into one statement:

    See for example What is the difference between a definition and a declaration? for a good explanation of the difference between declaration and definition.

    The Swift compiler treats the statement only as a declaration. Therefore the variable is not defined anywhere, causing the linker error.

    To solve the problem, you have to move the definition to an Objective-C file:

    // Constants.m:
#import "Constants.h"
NSString * const kColor005C98  = @"005C98";

    and change the declaration to an extern declaration:

    // Constants.h:
extern NSString * const kColor005C98;

    Alternatively, you can just remove the static modifier:

     NSString * const kColor005C98 = @"005C98";

    to make it work with Swift. The disadvantage is that when this line is included by multiple Objective-C files, all of them will define a globally visible symbol kColor005C98, causing "duplicate symbol" linker errors.

    Another alternative is to use a macro definition instead:

    #define kColor005C98 @"005C98"