Variable definition inside switch-case

Question

#pragma mark AlertView delegate
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
    NSUserDefaults *userdefault=[NSUserDefaults standardUserDefaults];

    switch (buttonIndex) {
        case 0:
            UIWebView *webview = [[UIWebView alloc]initWithFrame:CGRectMake(0, 0, 1024,768)];
            NSString * URLString =@"http://www.google.com";
            NSURL *URL = [NSURL URLWithString: URLString];
            NSURLRequest *request=[NSURLRequest requestWithURL:URL];
            [webview loadRequest:request]; // Use of undeclared identifier webview
            [self.view addSubview:webview]; // Use of undeclared identifier webview
            break;
        case 1:
            //if Yes button pressed on logout alert
            [self notificationAction];
            [userdefault removeObjectForKey:@"Login"];
            [userdefault synchronize];
            break;
        default:
            break;
    }
}

This is the code I am using to display a webpage. However in Xcode I get the following error on the 1st line of 1st case:

Expected Expression

Am I missing a header file that I'm suppose to import or am I doing something wrong?

Show more of your code above this snippet - the shown code is perfectly valid. You probably have a syntax error somewhere above it. — Undo, Nov 25 '13 at 17:59
Good advice: don't name your variables `nsrequest` and `nsurl`, those are easy to confuse with the types. Call them `urlString`, `url` and `request`. — , Nov 25 '13 at 18:01
Good Advice. I changed the name of the variables but the code error is being pointed to webview — software is fun, Nov 25 '13 at 18:12
It's also a good idea to keep your variable names *camelCase* with lowercase first letter. (eg. `url`, `urlString` etc.) — Filip Radelic, Nov 25 '13 at 18:35

Filip Radelic · Accepted Answer · 2013-11-25T18:34:15.870

2

When defining a variable on a first line inside a case, you have to wrap code of that case in { }

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
    NSUserDefaults *userdefault=[NSUserDefaults standardUserDefaults];

    switch (buttonIndex) {
        case 0:
        {
            UIWebView *webview = [[UIWebView alloc]initWithFrame:CGRectMake(0, 0, 1024,768)];
            NSString * URLString =@"http://www.google.com";
            NSURL *URL = [NSURL URLWithString: URLString];
            NSURLRequest *request=[NSURLRequest requestWithURL:URL];
            [webview loadRequest:request]; // Use of undeclared identifier webview
            [self.view addSubview:webview]; // Use of undeclared identifier webview
            break;
        }
        case 1:
            //if Yes button pressed on logout alert
            [self notificationAction];
            [userdefault removeObjectForKey:@"Login"];
            [userdefault synchronize];
            break;
        default:
            break;
    }
}

Why? Apparently C has problems with scope when defining a variable inside switch-case. Wrapping the code inside { } creates a new local scope.

edited Nov 25 '13 at 18:34

answered Nov 25 '13 at 18:17

Filip Radelic

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This is half true. You only need the curly braces if the 1st line after a `case X:` line is a variable declaration. If the 1st line isn't a variable declaration then you can have variable declarations on other lines without any curly braces. – rmaddy Nov 25 '13 at 18:30
True, updated my answer to include that. – Filip Radelic Nov 25 '13 at 18:32
1

To complete @rmaddy's half truth - a *switch statement* in C is a *computed goto* where the body of the switch is a single *block* and control is transferred to one of the *labels* within that block. A block is a sequence of *statements* and *declarations*, and any declarations are *scoped* to their containing block. And, finally :-), only *statements* can be labelled in C, not declarations. Placing the statements in `{` & `}` as in the answer forms a *compound statement* / *block* - as a statement it can be labelled, and as a block it limits the scope of the introduced variables. Isn't C fun! – CRD Nov 25 '13 at 19:10

Variable definition inside switch-case

1 Answers1