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?

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 — Yunus Nedim Mehel, Dec 06 '12 at 15:52

score 169 · Accepted Answer · edited May 23 '17 at 12:10

169

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.

edited May 23 '17 at 12:10

Community

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answered Jan 10 '10 at 11:28

Dan Olson

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1

Interesting. Didn't try the bracket approach. – Eimantas Jan 10 '10 at 11:30
Yes this fixes the problem. I was just running with xcode's code fill which doesn't use them. Thanks. – Ross Jan 10 '10 at 11:37
I've come across this problem before, I solved it using { } myself, good to see it was the correct solution. +1 for you Dan. – David Wong Jan 10 '10 at 11:51
25

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. – Peter Hosey Jan 10 '10 at 16:15
Thanks. This helped me. – Krishna Kanth Yenumula Apr 20 '22 at 18:01

score 25 · Answer 2 · edited May 23 '17 at 11:47

25

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.

edited May 23 '17 at 11:47

Community

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answered Jan 10 '10 at 16:08

Quinn Taylor

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score 3 · Answer 3 · answered Jan 20 '11 at 06:44

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:

answered Jan 20 '11 at 06:44

kiran kumar

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Compile Error with: switch, "expected expression before"

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