Objective-c: NSString to enum

Question

So, I\'ve got this definition:

typedef enum {
    red = 1,
    blue = 2,
    white = 3
} car_colors;

Then, I\'ve got a variable of type car_col

Answer 1

There are a lot of great answers to this here: Converting between C enum and XML

They are basically the same as Abizern's, but are a little cleaner and easier to work with if your app does this string-to-enum conversion a lot. There are solutions which keep the string and enum definitions together, and ways to make the conversions each a single, easy-to-read line of code.

Answer 2

// ...
typedef enum {
    One = 0,
    Two,
    Three
} GFN;
// ...
#define kGFNPrefix @"GFNEnum_"
// ...
+ (NSString *)gfnToStr:(GFN)gfn {
    return [NSString stringWithFormat:@"%@%d", kGFNPrefix, gfn];
}

+ (GFN)gfnFromStr:(NSString *)str {
    NSString *gfnStr = [str stringByReplacingOccurrencesOfString:kGFNPrefix withString:@""];
    return [gfnStr intValue];
}
// ...

My choice =)

Answer 3

here's an implementation using NSDictionary and the existing enum

in .h file:

typedef NS_ENUM(NSInteger, City) {
    Toronto         = 0,
    Vancouver       = 1
 };

@interface NSString (EnumParser)
- (City)cityEnumFromString;
@end

in .m file:

@implementation NSString (EnumParser)

- (City)cityEnumFromString{
    NSDictionary<NSString*,NSNumber*> *cities = @{
                            @"Toronto": @(Toronto),
                            @"Vancouver": @(Vancouver),
                            };
    return cities[self].integerValue;
}

@end

sample usage:

NSString *myCity = @"Vancouver";
City enumValue = [myCity cityEnumFromString];

NSLog(@"Expect 1, Actual %@", @(enumValue));

Answer 4

Rather than use an array, why not use a dictionary; You have the colour NSString as keys, and you return whatever NSNumber you want. Something like; (Long winded for clarity).

NSDictionary *carColourDictionary = @{@"Red": @1,
                                      @"Blue": @2,
                                      @"White": @3};

// Use the dictionary to get the number
// Assume you have a method that returns the car colour as a string:
// - (NSString *)colourAsString;
int carColour = carColourDictionary[object colourAsString];

Answer 5

I found the solution:

if ([car_color isEqualToString:@"1"])
        return red;
if ([tipo_pdi isEqualToString:@"2"])
        return blue;
if ([tipo_pdi isEqualToString:@"3"])
        return white;

But I don't like this 'if' style, what if I had a thousand colors? Isn't there a more automatic solution?

Answer 6

You could also put the values in an array.

NSArray *carColorsArray = @[@"red", @"blue", @"white"];

You can then use indexOfObject to get the index of a particular string.

car_colors carColor = [carColorsArray indexOfObject:@"blue"] + 1;