Can I declare variables inside an Objective-C switch statement?

Question

I think I'm going blind, because I can't figure out where the syntax error is in this code:

if( cell == nil ) {
    titledCell = [ [ [ TitledCell alloc ] initWithFrame:CGRectZero
     reuseIdentifier:CellIdentifier ] autorelease
    ];

    switch( cellNumber ) {
     case 1:
      NSString *viewDataKey = @"Name";
etc...

When I try to compile it, I'm getting an Error: syntax error before '*' token on the last line.

Sorry for such a basic question, but what am I missing?

Answer 1

Might it not be valid to declare a variable within a switch block?

Answer 2

I don't have a suitable Objective-C compiler on hand, but as long as the C constructs are identical:

switch { … } gives you one block-level scope, not one for each case. Declaring a variable anywhere other than the beginning of the scope is illegal, and inside a switch is especially dangerous because its initialization may be jumped over.

Do either of the following resolve the issue?

NSString *viewDataKey;
switch (cellNumber) {
    case 1:
        viewDataKey = @"Name";
    …
}

switch (cellNumber) {
    case 1: {
        NSString *viewDataKey = @"Name";
        …
    }
    …
}

Answer 3

You can't declare a variable at the beginning of a case statement. Make a test case that just consists of that and you'll get the same error.

It doesn't have to do with variables being declared in the middle of a block — even adopting a standard that allows that won't make GCC accept a declaration at the beginning of a case statement. It appears that GCC views the case label as part of the line and thus won't allow a declaration there.

A simple workaround is just to put a semicolon at the beginning of the case so the declaration is not at the start.

Answer 4

In C you only can declare variables at the begining of a block before any non-declare statements.

{
   /* you can declare variables here */

   /* block statements */

   /* You can't declare variables here */
}

In C++ you can declare variables any where you need them.