How do switch statements work in Objective-C?

Question

I am using switch statements in Objective-C, and when I nest a switch statement inside another switch statement, a lot of errors are being found by the compiler. So my general question is how do switch statements affect what methods I can call, and what type of behavior is causing the compiler to generate errors?

switch ([indexPath section]) 
{
    case 0:
        cell.textLabel.text = [infoKeysArray objectAtIndex:indexPath.row];
        CountdownFormatter *formatter = [[CountdownFormatter alloc] init];
        switch (indexPath.row) {
            case 0:
                cell.detailTextLabel.text = [formatter stringForCountdownInterval:taskInfo.duration];
                break;
            case 1:
                cell.detailTextLabel.text = [formatter stringForCountdownInterval:taskInfo.elapsedTime];
            default:
                break;
        }
        [formatter release];
        break;
    case 1:
        cell.textLabel.text = [actionsKeysArray objectAtIndex:indexPath.row];
        //NSArray *segments = [NSArray arrayWithObjects:@"Low", @"Medium", @"High", nil];
        switch (indexPath.row) {
            case 0:
                cell.detailTextLabel.text = priority;
                [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator];
                break;
            case 1:
                [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator];
                UISwitch *switch = [[UISwitch alloc] init];
                break;
            case 2:

                break;
            default:
                break;
        }
        break;
    case 2:
        cell.textLabel.text = [detailsKeysArray objectAtIndex:indexPath.row];
        break;
    default:
        break;
}

Here is where I am having issues. Why can I not declare a UISwitch inside this nested switch statement? I know I wrote [[UISwitch alloc] init] but the compiler is flagging it as an error. Any reason that would happen?

There is nothing wrong with nesting switch statements. Why don't you post your code and error message so we can try to fix it? — ughoavgfhw, Jan 25 '12 at 23:17
I was trying not to just have people directly edit my code, I'd rather figure it out for myself, but clearly something is going on here of which I am not aware. — gurooj, Jan 25 '12 at 23:30

score 2 · Accepted Answer · edited May 23 '17 at 12:20

2

I can't say it any better than this answer Why can't variables be declared in a switch statement?.

The issue is where/when you are declaring variables and the scope they are in.

edited May 23 '17 at 12:20

Community

1
1

answered Jan 25 '12 at 23:38

Paul.s

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Yea, I stumbled upon something similar. I didn't realize that was the issue. I ended up asking the wrong question, but arriving at the correct answer. – gurooj Jan 25 '12 at 23:46

ta.speot.is · Answer 2 · 2012-01-25T23:36:19.990

when I nest a switch statement inside another switch statement, a lot of errors are being found by the compiler

Works fine for me:

int main()
{
    int x = 1;
    int y = 2;

    switch(x)
    {
    case 1:
       switch(y)
       {
       case 2:
         printf("Hello!\n");
       }
    }

    return 0;
}

So my general question is how do switch statements affect what methods I can call

They don't.

and what type of behavior is causing the compiler to generate errors?

The programmer's behaviour.

EDIT - In response to the code you posted, without being able to compile or see what the error is I would suspect:

case 1:
        [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator];
        UISwitch *switch = [[UISwitch alloc] init];
        break;

could be:

case 1:
{
        [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator];
        UISwitch *myswitch = [[UISwitch alloc] init];
        break;
}

Note the braces and the choice of naming the variable something other than a keyword.

It has to do with declaring variables inside the scope of a switch statement; basically, it is illegal to do so. — gurooj, Jan 25 '12 at 23:47

score 1 · Answer 3 · answered Jan 25 '12 at 23:18

1

Switch statements have no effect whatsoever on obj-c. They're pure C constructs, and work in Obj-C exactly as they do in C. As for errors, you likely have some sort of syntactic error if you're getting compiler errors when nesting switch statements.

answered Jan 25 '12 at 23:18

Lily Ballard

182,031
33
381
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1

I'd like to think that writing a `switch` statement would have *some effect*. – ta.speot.is Jan 25 '12 at 23:21

How do switch statements work in Objective-C?

3 Answers3