NSString+Inflections.m

//
//  NSString+Inflections.m
//  Zap
//
//  Created by Stevie Graham on 28/10/2013.
//

#import "NSString+Inflections.h"

@implementation NSString (Inflections)
- (NSString *)snakeCaseString {
  NSScanner * scanner = [NSScanner scannerWithString:self];
  scanner.caseSensitive = YES;

  NSCharacterSet * upper = [NSCharacterSet uppercaseLetterCharacterSet];
  NSCharacterSet * lower = [NSCharacterSet lowercaseLetterCharacterSet];

  NSString * string;
  NSMutableString * output = [NSMutableString string];

  while (!scanner.isAtEnd) {
    if ([scanner scanCharactersFromSet:upper intoString:&string])
      [output appendString:[string lowercaseString]];

    if ([scanner scanCharactersFromSet:lower intoString:&string]) {
      [output appendString:string];
      if (!scanner.isAtEnd) [output appendString:@"_"];
    }
  }
  
  return [NSString stringWithString:output];
}

- (NSString *)llamaCaseString {
  NSArray         * components = [self componentsSeparatedByString:@"_"];
  NSMutableString * output     = [[components firstObject] mutableCopy];
  NSRange           tail       = NSMakeRange(1, [components count] - 1);

  for (NSString * component in [components subarrayWithRange:tail])
    [output appendString:[component capitalizedString]];

  return [NSString stringWithString:output];
}
@end

ZPStringTranformers.m

//
//  ZPStringTranformers.m
//  Zap
//
//  Created by Stevie Graham on 28/10/2013.
//

#import "ZPStringTranformers.h"
#import "NSString+Inflections.h"
#import <NSValueTransformer+TransformerKit.h>

NSString * const ZPSnakeCaseStringTransformerName = @"ZPSnakeCaseStringTransformer";
NSString * const ZPLlamaCaseStringTransformerName = @"ZPLlamaCaseStringTransformer";

@implementation ZPStringTranformers
+ (void)load {
  @autoreleasepool {
    [NSValueTransformer registerValueTransformerWithName:ZPSnakeCaseStringTransformerName transformedValueClass:[NSString class] returningTransformedValueWithBlock:^id(id value) {
      return [value snakeCaseString];
    }];
    
    [NSValueTransformer registerValueTransformerWithName:ZPLlamaCaseStringTransformerName transformedValueClass:[NSString class] returningTransformedValueWithBlock:^id(id value) {
      return [value llamaCaseString];
    }];
  }
}
@end