Get #define of type UIColor from NSString

Question

I have defined the following constants, each of which represents a UIColor:

// Purple
#define PURPLE_COLOR_DARK  [UIColor colorWithRed: 0.42 green: 0.25 blue: 0.60 alpha: 1.0]
#define PURPLE_COLOR_LIGHT [UIColor colorWithRed: 0.78 green: 0.47 blue: 0.72 alpha: 1.0]

// Blue
#define BLUE_COLOR_DARK  [UIColor colorWithRed: 0.00 green: 0.46 blue: 0.70 alpha: 1.0]
#define BLUE_COLOR_LIGHT [UIColor colorWithRed: 0.00 green: 0.75 blue: 0.88 alpha: 1.0]

// Magenta
#define MAGENTA_COLOR_DARK  [UIColor colorWithRed: 0.75 green: 0.00 blue: 0.28 alpha: 1.0]
#define MAGENTA_COLOR_LIGHT [UIColor colorWithRed: 1.00 green: 0.32 blue: 0.61 alpha: 1.0]

Question

How can I use an NSString like @"purple" , @"blue" or @"magenta" to get the related "X_COLOR_DARK" or "X_COLOR_LIGHT" constant? Is it even possible to do so directly?

Example

This is wrong, but should provide a clearer picture of what I'm asking. In this example, I have the string @"blue" and want to derive the BLUE_COLOR_DARK and BLUE_COLOR_LIGHT color values.

NSString *color = @"blue";
UIColor *darkColor = (UIColor *)[[NSString stringWithFormat: @"%@_COLOR_DARK", color] uppercaseString];

// Debugging    
NSLog(@"%@", darkColor); // BLUE_COLOR_DARK
NSLog(@"%hhd", [lightColor isKindOfClass: [UIColor class]]);  // 0
NSLog(@"%hhd", [lightColor isKindOfClass: [NSString class]]); // 1

Follow-Up

Note that UIColor is not necessarily relevant to answering the question, though it does help for my situation. More specifically, I'm asking if a string matching a defined name (eg @"PURPLE_COLOR_DARK" and #define PURPLE_COLOR_DARK ) can be interpreted as the defined name instead of using the defined name directly.

Answer 1

Ditch the #defines. And use a UIColor category and NSSelectorFromString like outlined in this answer .

Or, create a NSDictionary where the keys are the names of your colors and the objects are your colors. You can then get UIColor by name.

Eg:

NSDictionary *colors = @{ @"purple_dark"  : PURPLE_COLOR_DARK,
                          @"purple_light" : PURPLE_COLOR_LIGHT };

NSString *colorName = @"purple";

NSString *lightColorName = [colorName stringByAppendingString:@"_light"];
NSString *darkColorName = [colorName stringByAppendingString:@"_dark"];

UIColor *lightColor = colors[lightColorName];
UIColor *darkColor = colors[darkColorName];

---

you can't use the #defined names directly because those names don't exist in the compiled code. During compilation the preprocessor will replace all occurrences of PURPLE_COLOR_DARK with [UIColor ...]

Answer 2

You can create category of UIColor.

UIColor+CustomColors.h

+ (UIColor *)redFill;

UIColor+CustomColors.m

+ (UIColor *)redFill
{
    return [UIColor colorWithRed:240.0 / 255.0 green:36.0 / 255.0 blue:0.0 / 255.0 alpha:1.0];
}

Now use this category in your class:

NSArray *color = @[[UIColor redFill], ...etc];

Understand category