PrepareForSegue mystery

Question

I\'ve got a prepareForSegue method in two different VCs. One uses an if statement, while the other is intended to use a switch. The code is virtually i

Answer 1

To solve the second error, try adding braces in your switch-case to define a context to the variables:

-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread];
    [SearchSpecs MR_truncateAllInContext:localContext];
    [localContext MR_saveToPersistentStoreAndWait];

    switch ([sender tag])
    {
        case aVsAButton_tag:
            {
                UINavigationController *navController = (UINavigationController *)segue.destinationViewController;
                AvsAViewController *aVSaVC = (AvsAViewController *)navController.topViewController;
                aVSaVC.delegate = self;
                SearchSpecs *thisSpec = (SearchSpecs *)[SearchSpecs MR_createInContext:localContext];
                aVSaVC.currentSpec = thisSpec;
            }
            break;

        default:
            break;
    }

}

Answer 2

There are two separate problems here.

You can declare a variable in C/Objective-C in a switch-statement (without the need for an additional { ... } scope), but not immediately following a label. To solve this problem it is sufficient to insert a semicolon after the label:

switch (i) {
    case 0: ;
        int i;
        // ...
        break;

    default:
        break;
}

Only if you declare Objective-C objects and compile with ARC, then you have to introduce an additional scope:

switch (i) {
    case 0: {
        NSObject *obj;
        // ...
        } break;

    default:
        break;
}

The reason is that the ARC compiler needs to know the precise lifetime of the object.

Answer 3

In C/Objective-C, you cannot declare variables in a switch statement like that. If you want to declare variables for use in a specific case of a switch statement, you can put all the code for that case in a statement block:

switch ([sender tag])
{
    case aVsAButton_tag:
    {
        UINavigationController *navController = (UINavigationController *)segue.destinationViewController;
        AvsAViewController *aVSaVC = (AvsAViewController *)navController.topViewController;
        aVSaVC.delegate = self;
        SearchSpecs *thisSpec = (SearchSpecs *)[SearchSpecs MR_createInContext:localContext];
        aVSaVC.currentSpec = thisSpec;
    }
        break;

    default:
        break;
}