This is tested and works well
NSWorkspace *nsSharedWorkspace = [NSWorkspace sharedWorkspace];
NSString *nsAppPath = [nsSharedWorkspace fullPathForApplication:appName];
NSBundle *nsAppBundle = [NSBundle bundleWithPath: nsAppPath];
NSDictionary *nsAppInfo = [nsAppBundle infoDictionary];
//Now you can print all dictionary to view all its contents and pick which you want
NSLog(@"%@",nsAppInfo);
//or you can get directly using following methods
NSLog(@"%@",[nsAppInfo objectForKey:@"CFBundleShortVersionString"]);
NSLog(@"%@",[nsAppInfo objectForKey:@"CFBundleVersion"]);
Dont forget to add AppKit framework