Declaring variables inside a switch statement

I saw a few answers to this issue, and I get it — you can't declare and assign variables inside a `switch`. But I'm wondering if the following is correct at throwing an error saying

> error: expected expression before 'int'

Code:

switch (i) {
case 0:
int j = 1;
break;
}

Why would putting a call to `NSLog()` before it result in no errors?

switch (i) {
case 0:
NSLog(@"wtf");
int j = 1;
break;
}

I've run into this issue before, and the conclusion was that you just put the code inside a block.

switch (i) {
case 0:
{
int j = 1;
break;
}
}

You actually _can_ declare variables within a switch if you do it according to the syntax of the language. You're getting an error because "`case 0:`" is a label, and in C it's illegal to have a **declaration** as the first statement after a label — note that the compiler expects an **expression**, such as a method call, normal assignment, etc. (Bizarre though it may be, that's the rule.)

When you put the NSLog() first, you avoided this limitation. You can enclose the contents of a case in { } braces to introduce a scoping block, or you can move the variable declaration outside the switch. Which you choose is a matter of personal preference. Just be aware that a variable declared in { } braces is only valid within that scope, so any other code that uses it must also appear within those braces.

---

**Edit:**

By the way, this quirk isn't as uncommon as you might think. In C and Java, it's also illegal to use a local variable declaration as the lone statement (meaning "not surrounded by braces) in a **for**, **while**, or **do** loop, or even in **if** and **else** clauses. (In fact, this is covered in puzzler #55 of ["Java Puzzlers"][1], which I highly recommend.) I think we generally don't write such errors to begin with because it makes little sense to declare a variable as the only statement in such contexts. With **switch** / **case** constructs, though, some people omit the braces since the **break** statement is the critical statement for control flow.

To see the compiler throw fits, copy this horrific, pointless snippet into your (Objective-)C code:

if (1)
int i;
else
int i;
for (int answer = 1; answer <= 42; answer ++)
int i;
while (1)
int i;
do
int i;
while (1);

Yet another reason to always use { } braces to delimit the body of such constructs. :-)


[1]:

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Another simple workaround I use is to add an empty expression (semicolon) before the declaration. This avoids limiting the variable scope to a code block (or having some case statements with code blocks and some without).

switch (i) {
case 0:;
int j = 1;
break;
}