Compile Error with: switch, "expected expression before"

Question

Cut to the chase I have recreated my problem as it is fairly self explanatory.

this complies without error:

switch (n) {
    case 1:
        NSLog(@"");
        NSString *aStr;
        break;
    default:
        break;
    }

this compiles with error and it's only missing the NSLog():

switch (n) {
    case 1:
        NSString *aStr;
        break;
    default:
        break;
    }

it throws an error at compile "Expected expression before 'NSString'"

Am I missing something here?

Bruyn

See <https://mcmap.net/q/46891/-weird-switch-error-in-obj-c/…> – Alley

I remember a switch/case statement with a similar error, it used to disappear when I add a comment somewhere within the case block.. Magic – Eighteenth

Answer 1

In normal C you'd have to enclose this in brackets in both cases. I suspect this may fix your problem:

case 1:
{
    NSLog(@"");
    NSString *aStr;
    break;
}

See this SO question for more info.

Another way to get around this problem is to put a statement between the case label and the first declaration as you've done in your working example above. See the comments and Quinn Taylor's answer for more info.

Nemhauser

Interesting. Didn't try the bracket approach. – Stretcher

Yes this fixes the problem. I was just running with xcode's code fill which doesn't use them. Thanks. – Bruyn

I've come across this problem before, I solved it using { } myself, good to see it was the correct solution. +1 for you Dan. – Insensate

You don't necessarily have to use brackets. Putting an empty statement (;) after the case label works, too. The reason for the error and the reason why both solutions work is that a label, including a case label, can only precede a statement. Declarations aren't statements in C (C99 §6.7, §6.8, §6.8.2) and Objective-C, so you can't put a label immediately before a declaration. Thus the solutions: Either put a statement (such as ; or NSLog(@"");) between the label and declaration, or wrap the declaration inside a compound statement (the brackets) following the label. – Chaff

Answer 2

You can't declare a variable as the first statement in a case without brackets, and in many other contexts in C-based languages. See Declaring variables inside a switch statement for details.

Fenske

Answer 3

case 0: {
    Loading my nib file;
    break; 
}
case 1: {
    Loading another nib file;
    break; 
}
Note that if you don't have an assignment (x = y) right after the case it won't be a problem. For example:

Tryck