Why do my switch cases sometime need braces in Objective-C?

Question

Sometimes Xcode will show an error "Expected expression" on the line after a case. For example, Xcode is pointing to UserContentViewController with a red arrow:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    switch (indexPath.row) {
        case IndexVideo: 
            UserContentViewController* detailViewController = [[UserContentViewController alloc] initWithUser:self.user];
            [self.navigationController pushViewController:detailViewController animated:YES];
            break;

    }
}

If I put braces around my case, the error is gone. Firstly, I want to know what is the problem with not using braces. I've never used braces in cases in any other language. Secondly, why does Xcode only complain about my cases on rare occasions? I can't quite discern what type of code triggers this error.

possible duplicate of [Why can't variables be declared in a switch statement?](http://stackoverflow.com/questions/92396/why-cant-variables-be-declared-in-a-switch-statement) or [Can I declare variables inside an Objective-C switch statement?](http://stackoverflow.com/questions/1115304/can-i-declare-variables-inside-an-objective-c-switch-statement) or [Declaring variables inside a switch statement](http://stackoverflow.com/questions/1231198/declaring-variables-inside-a-switch-statement). Just to name three ;-) — Matthias Bauch, Jul 10 '13 at 22:39

Wain · Accepted Answer · 2013-07-11T11:46:35.713

14

Basically, if you want to declare a variable you need to add the braces to define scope.

ARC also adds some requirements (or, rather, stricter requirements) to define scope (so you may get a number of "switch case is in protected scope" errors to fix when upgrading an older codebase). This is because ARC needs to know in detail when a variable isn't / can't be referred to any more so that it can deal with the release correctly.

Everything relates back to giving the compiler enough information about the scope of declared variables. Should they be part of a single case, or multiple cases...

edited Jul 11 '13 at 11:46

answered Jul 10 '13 at 22:32

Wain

118,658
15
128
151

8

sure it is because of ARC? I think it is even needed in plain C. – vikingosegundo Jul 10 '13 at 22:37
http://cboard.cprogramming.com/c-programming/109187-declare-variable-case-statement.html – vikingosegundo Jul 10 '13 at 22:39
Without braces, why is it not understood that I want the scope to be same as the switch? – Pwner Jul 10 '13 at 22:40
@Pwner C is a very low level language, so the compiler assumes nothing. If it doesn't see braces, it means you didn't ask for a scope. It won't put it there for you. – Greg Jul 10 '13 at 23:17
I think you still need braces without ARC – Bryan Chen Jul 11 '13 at 02:21
This answer proves, that you dont need to answer correctly to get reputation. THIS IS NOT AT ALL RELATED TO ARC! – vikingosegundo Jul 11 '13 at 11:22
@vikingosegundo, apologies for the delay, I've updated to clarify the ARC side of things. – Wain Jul 11 '13 at 11:27
It would be nice, if you'd explain why the braces are needed. Or if you would vote for closure as duplicate, as the answer was given before. – vikingosegundo Jul 11 '13 at 11:36
Actually, all you need is to add a `;` after the `:`. – Sulthan Jul 11 '13 at 11:51

Why do my switch cases sometime need braces in Objective-C?

1 Answers1

Linked