Question

I try to understand how to define a list of valid elements for a class:
Let’s say i have a class People and i need to accept only 3 strings as possible valid names
@"Luke",@"Paul",@"Mark".

I thought to use a combination of enum and NSDictionary this way (but i’m obviously not sure about the correctness of this method):

//INTERFACE*********************
typedef enum {  
 Luke,Paul,Mark
}ValidName;

@interface Person : NSObject{  
  // some code

}

@end


//IMPLEMENTATION*******************
@interface Person(private){
 NSMutableDictionary *_validNamesDict;
}
@end

@interface Person:NSObject
- (id)init
{
    self = [super init];
    if (self) {
        _validNamesDict = [[NSMutableDictionary alloc] init];
        [_validNamesDict setObject: @"Luke" forKey:[NSNumber numberWithInt: Luke]];
        [_validNamesDict setObject: @"Paul" forKey:[NSNumber numberWithInt: Paul]];
        [_validNamesDict setObject: @"Mark" forKey:[NSNumber numberWithInt: Mark]];
    }

    return self;
}

//Some code .... 

Now in the rest of the class i refer to this name with:

[_validNameDict objecWithKey:[NSNumber numberWithInt: Luke]]; 

I’m pretty sure this is not the best method. Could you suggest me a valid way to manage this situation ? I read something about the use of extern keyword and definition to static variable into class… is it maybe a better method?

Answer 1

I think what you want here is a set, not a map–that is, an NSSet, not an NSDictionary.

Let’s say you have the set validNames and you want to determine if the name n is in the set. Once your set is initialized, just do the following:

BOOL nameIsValid = [validNames containsObject:n];