Not allowing to use Constant defined in Objective C header file in swift class. Undefined symbols for architecture armv7
arm7, objective-c, swift
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:
- A variable declaration which introduces an identifier and describes its type, and
- a variable definition which actually instantiates/implements this identifier.
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"
Problem
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)