How to know at run-time whether your code runs inside an iOS extension

extension

NSDictionary *extensionInfo = [NSBundle.mainBundle objectForInfoDictionaryKey:@"NSExtension"];
NSString *extensionPointIdentifier = extensionInfo[@"NSExtensionPointIdentifier"];
if ([extensionPointIdentifier isEqualToString:@"com.apple.watchkit"]) {
    NSLog(@"WatchKit extension");
} else if ([extensionPointIdentifier isEqualToString:@"com.apple.widget-extension"]) {
    NSLog(@"Widget extension");
} else if (extensionPointIdentifier == nil) {
    NSLog(@"iOS app");
} else {
    NSLog(@"Unknown extension type");
}