Efficient way to create ordered set of string values in Objective-C

I want to create an enum-like set of strings in a way that will also provide me the ability开发者_JS百科 to order them by their ordinal value and NOT by alphabetic value. for example:

"Extremely Low" = 0

"Very Low" = 1

"Low" = 2

"Medium = 3

"High" = 4

and so on.

I know that in Java and C# for example, enum types can have a value besides their ordinal value.

Is there any way to achieve the same goal in Objective-C?

Thanks!

I don't know a direct way to do that. However, you can define an Obj-C class like this:

@interface EnumLike : NSObject
{
    NSString* title;
    NSInteger value;
}

@property (nonatomic, readonly) NSString* title;
@property (nonatomic, readonly) NSInteger value;

// Something like enum
+ (id)extremelyLow;
+ (id)veryLow;
...
+ (id)high;
};

Except working with the switch this can do the job. I use similar types from time to time to declare some "enums" for the user since a list of such instances can be binded to an NSArrayController and used in the UI.

Just keep the strings for I/O and use an enum for all your computations. For example, define your enum:

typedef enum { ExtremelyLow, VeryLow, ... High } Rating;

You can use this enum in switch statements etc. Now you can use an NSArray or just a simple C-array to map from enum literals to strings:

NSString *RatingToString[] = { @"Extremely Low", @"Very Low", ..., @"High" };

Rating myRating;
NSString *strMyRating = RatingToString[myRating];

Going from the string version to the enum is more involved, you can use the same RatingToString array and do appropriate comparisons (case-insensitive maybe, fuzzy etc.). You could also use an NSDictionary:

NSDictionary StringToRating = [NSDictionary dictionaryWithObjectsAndKeys: RatingToString[ExtremelyLow], [NSNumber numberWithInt:ExtremelyLow, ..., nil];

Now a lookup will do an exact match on your string and return a Rating wrapped as an NSNumber.

You can use a class like Gobra suggested or an array of c structs:

typedef struct {
    int                      type;
    NSString                 *desc;
} NXENumToNSString;



NXENumToNSString kNXGMWidgetTypes[] = {
    {1, @""},
    {2, @"imageGallery"},
    {3, @"dotImageGallery"},
    {4, @"video"},
    {5, @"webView"},
    {6, @"image"}
};

NSInteger  
intToStringForArray(NXENumToNSString *buffer, size_t length, NSString *str) 
{
    int result = NSIntegerMin;
    NXENumToNSString *scan, *stop;  
    scan = buffer;
    stop = scan + length;
    while (scan < stop) {
        if ([scan->desc isEqualToString:str]) {
            result = scan->type;
            break;
        }
        scan++;
    }
    return result;
}

then you can do something like this:

 size_t l = sizeof(kNXGMWidgetTypes) / sizeof(NXENumToNSString);
 NSInteger result = intToStringForArray(kNXGMWidgetTypes, l, str);