Question

I would like to use something like:

if (foo>0){
 typedef enum {  
   Form_FirstName = 0,
   Form_NamePrefix,
   Form_LastName,
   Form_Email,
   Form_Phone
 } Form; 
} else {
   typedef enum {
   Form_FirstName = 0,
   Form_LastName,
   Form_Phone
 } Form;
}

Can this be done? Where should I do this? In the .m or in the .h? I want to use this for an UITableView.

Answer 1

No.

Firstly, enumerations are compile type constructs.

Secondly, you have a scoping issue. Because you are defining the enumeration type within the scope of the if and the else. It will not have visibility outside of the if..else.. statement.

You’ll need to find a different way to differentiate your indexing based on a state.

Updating based on OP’s follow on question:

OK, you need a map of some sort. For example you could do:

Define your enumeration.

enum {
   Form_FirstName = 0,
   Form_NamePrefix,
   Form_LastName,
   Form_Email,
   Form_Phone
};

Assuming your class has an indexes ivar with the usual @property and @synthesize, set up your indexes:

if (foo>0) {
    self.indexes = [NSArray arrayWithObjects:[NSNumber numberWithInt:Form_FirstName],[NSNumber numberWithInt:Form_NamePrefix],[NSNumber numberWithInt:Form_LastName],[NSNumber numberWithInt:Form_Email],[NSNumber numberWithInt:Form_Phone],nil];
}
else {
    self.indexes = [NSArray arrayWithObjects:[NSNumber numberWithInt:Form_FirstName],[NSNumber numberWithInt:Form_LastName],[NSNumber numberWithInt:Form_Email],[NSNumber numberWithInt:Form_Phone],nil];
}

Elsewhere, when you need to translate an enumerated field to an index:

NSInteger index = [self.indexes indexOfObject:[NSNumber numberWithInt:<Form Enumeration Value>]];