'break' statement when using curly braces in switch-case

问题

I use curly braces with all of my switch case statements in C/Objective-C/C++

I had not, until a few moments ago, considered whether including the break; statement inside the braces was good or bad practice. I suspect that it doesn't matter, but I figure it is still worth asking.

    switch (foo) {
        case 1: {
            // stuff
            break;
        }

        default: {
            break;
        }
    }

vs

    switch (foo) {
        case 1: {
            // stuff
        } break;

        default: {
            // stuff
        } break;
    }

回答1:

Short answer: it doesn't matter.

回答2:

Just a give a slightly more detailed answer...

The official C99 specification says the following about the break statement:

A break statement terminates execution of the smallest enclosing switch or iteration statement.

So it really doesn't matter. As for me, I put the break inside the curly braces. Since you can also have breaks in other places inside your curly braces, it's more logical to also have the ending break inside the braces. Kind of like the return statement.

回答3:

There's tons of different coding styles of how to combine curly braces and switches. I'll use the one I prefer in the examples. The break statement breaks out of the innermost loop or switch statement, regardless of location. You could for example have multiple breaks for a single case:

switch (foo) {
case 1:
    {
        if (bar)
            break;
        bar = 1;
        ...
    }
    break;
}

Note that you can also put the cases anywhere, though that is somewhat considered bad practice. The case label is very much like a goto label. It has happened that I've written something like this:

switch (foo) {
case 1:
    bar = 1;
    if (0) {
case 2:
        bar = 2;
    }
    ...
    break;
}

but use it with care.

回答4:

You probably don't want the curlies in the first place unless you need them for lexical scope. The first example looks better to me, but I suppose the real answer is that it's a matter of taste.

回答5:

As clearly stated, this is just a matter of personal style, but I always put the break statement outside the braces: putting the break before the closing brace seems to me to jump out a compound statement thus slightly increasing the spaghetti code feeling.

来源：https://stackoverflow.com/questions/7374486/break-statement-when-using-curly-braces-in-switch-case