SDLEnum Redesign Example

SDLEnum.h

#import <Foundation/Foundation.h>

@interface SDLEnum : NSObject

+ (NSDictionary *)map;
+ (NSUInteger)transformString:(NSString *)stringValue;
+ (NSString *)transformEnum:(NSUInteger)enumValue;

@end

SDLEnum.m

#import "SDLEnum.h"

@implementation SDLEnum

+ (NSDictionary *)map {
    @throw [NSException exceptionWithName:@"SDLAbstractMethodException" reason:[NSString stringWithFormat:@"Cannot call %s on %@, must be called on a subclass", __FUNCTION__, self.class] userInfo:nil];
}

+ (NSUInteger)transformString:(NSString *)stringValue {
    __block NSNumber *result = nil;
    
    [[self map] enumerateKeysAndObjectsUsingBlock:^(NSNumber *key, NSString *obj, BOOL *stop) {
        if ([obj isEqualToString:stringValue]) {
            result = key;
            *stop = YES;
        }
    }];
    
    return result.unsignedIntegerValue ?: NSNotFound;
}

+ (NSString *)transformEnum:(NSUInteger)enumValue {
    return [self map][@(enumValue)];
}

- (id)objectAtIndexedSubscript:(NSUInteger)idx {
    return [self.class transformEnum:idx];
}

- (id)objectForKeyedSubscript:(id<NSCopying, NSObject>)key {
    if ([key isKindOfClass:[NSString class]]) {
        return @([self.class transformString:(NSString *)key]);
    }
    
    return nil;
}

@end

SDLEnumAppHMIType.h

#import <Foundation/Foundation.h>

#import "SDLEnum.h"


typedef NS_ENUM(NSUInteger, SDLAppHMIType) {
    SDLEnumAppHMITypeDefault,
    SDLEnumAppHMITypeCommunication,
    SDLEnumAppHMITypeMedia,
    SDLEnumAppHMITypeMessaging,
    SDLEnumAppHMITypeNavigation,
    SDLEnumAppHMITypeInformation,
    SDLEnumAppHMITypeSocial,
    SDLEnumAppHMITypeBackgroundProcess,
    SDLEnumAppHMITypeTesting,
    SDLEnumAppHMITypeSystem
};

@interface SDLEnumAppHMIType : SDLEnum

@end

SDLEnumAppHMIType.m

#import "SDLEnumAppHMIType.h"

@implementation SDLEnumAppHMIType

+ (NSDictionary *)map {
    static NSDictionary *dict;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        dict = @{@(SDLEnumAppHMITypeDefault): @"DEFAULT",
                 @(SDLEnumAppHMITypeCommunication): @"COMMUNICATION"};
    });
    
    return dict;
}

@end