How do I lookup a string constant at runtime in Objective-C?

Question

My company develops an advertising SDK that mediates other ad networks. At runtime, it checks if the other ad networks are present by using NSClassFromString , and sends those classes messages if they're present.

This works fine for Objective-C objects, but how can I load a string constant at runtime? In this case, I want to check the version of an SDK that is only available through a string constant ( extern NSString* VungleSDKVersion; )

Answer 1

You can use CFBundleGetDataPointerForName to lookup a constant's value at runtime

NSString *lookupStringConstant(NSString *constantName) {
    void ** dataPtr = CFBundleGetDataPointerForName(CFBundleGetMainBundle(), (__bridge CFStringRef)constantName);
    return (__bridge NSString *)(dataPtr ? *dataPtr : nil);
}

Example use:

NSString *version = lookupStringConstant(@"VungleSDKVersion");
NSLog(@"Version = %@",version);