Funny switch error in iOS

Could you try those two codes ? The first one raises an error, not the second one. I'd like to know if it's because of my XCode version, and if not, why is it happening.

        int typeNumber = 4;
        switch (typeNumber) {
            case typeNumberEvent:
                NSString myString;
                break;
            case typeNumberAd:
                NSURL myURL;
                break;
            default:
                NSNumber myNumber;
      开发者_开发技巧          break;
        }

        int typeNumber = 4;
        switch (typeNumber) {
            case typeNumberEvent:
                NSLog(@"hello");
                NSString myString;
                break;
            case typeNumberAd:
                NSLog(@"hello");
                NSURL myURL;
                break;
            default:
                NSLog(@"hello");
                NSNumber myNumber;
                break;
        }

The compiler throws error if you try to create a variable at the first line of case.

Just enclose the case block with braces. Everything will be alright.

case typeNumberEvent: {
        NSString myString;
        break;
}

If you declare variables inside a case block, you should declare that block with curly braces. Your example would become:

    int typeNumber = 4;
    switch (typeNumber) {
        case typeNumberEvent:
            {
                NSString myString;
                break;
            }
        case typeNumberAd:
            {
                NSURL myURL;
                break;
            }
        default:
            {
                NSNumber myNumber;
                break;
            }
    }

This answer sums it up nicely, too: Can I declare variables inside an Objective-C switch statement?