Question

Im digging for ways to enum objc object such as NSString, I remember there a new feature in a version of Xcode4+ which offering a new way to enum , but not clearly. Anyone know that?

Answer 1

OK, I answered myself. Guess I make a mistake.

This is the new feature I mentioned above:

typedef enum Language : NSUInteger{
     ObjectiveC,
     Java, 
     Ruby, 
     Python, 
    Erlang 
}Language;

It’s just a new syntax for enum in Xcode 4.4, but I’m so foolish to think we can exchange “NSUInteger” to “NSString”.

So here is the way I found that works:

http://longweekendmobile.com/2010/12/01/not-so-nasty-enums-in-objective-c/

// Place this in your .h file, outside the @interface block
typedef enum {
    JPG,
    PNG,
    GIF,
    PVR
} kImageType;
#define kImageTypeArray @"JPEG", @"PNG", @"GIF", @"PowerVR", nil

...

// Place this in the .m file, inside the @implementation block
// A method to convert an enum to string
-(NSString*) imageTypeEnumToString:(kImageType)enumVal
{
    NSArray *imageTypeArray = [[NSArray alloc] initWithObjects:kImageTypeArray];
    return [imageTypeArray objectAtIndex:enumVal];
}

// A method to retrieve the int value from the NSArray of NSStrings
-(kImageType) imageTypeStringToEnum:(NSString*)strVal
{
    NSArray *imageTypeArray = [[NSArray alloc] initWithObjects:kImageTypeArray];
    NSUInteger n = [imageTypeArray indexOfObject:strVal];
    if(n < 1) n = JPG;
    return (kImageType) n;
}

FYI. The original author of the second example code created a category for enum handling. Just the thing for adding to your very own NSArray class definition.

@interface NSArray (EnumExtensions)

- (NSString*) stringWithEnum: (NSUInteger) enumVal;
- (NSUInteger) enumFromString: (NSString*) strVal default: (NSUInteger) def;
- (NSUInteger) enumFromString: (NSString*) strVal;

@end

@implementation NSArray (EnumExtensions)

- (NSString*) stringWithEnum: (NSUInteger) enumVal
{
    return [self objectAtIndex:enumVal];
}

- (NSUInteger) enumFromString: (NSString*) strVal default: (NSUInteger) def
{
    NSUInteger n = [self indexOfObject:strVal];
    if(n == NSNotFound) n = def;
    return n;
}

- (NSUInteger) enumFromString: (NSString*) strVal
{
    return [self enumFromString:strVal default:0];
}

@end