RKObjectMapping+TransformationMapping.h

//
//  RKObjectMapping+TransformationMapping.h
//  OtherScreen
//
//  Created by Luke Redpath on 05/10/2012.
//  Copyright (c) 2012 Mark Rickert. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <RestKit/RestKit.h>

typedef  NSString* (^RKObjectMappingSourceKeyTransformationBlock)(NSString *sourceKey);

/* This category allows mappings to be configured using a block to transform
 the source key into the destination key.
 
 The use case for this is when your source keys map to your destination keys using
 a common pattern, e.g. snake_case attributes mapping to Objective-C style lowerCamelCase
 attributes.
 
 Configuring these kind of mappings is tedious as the transformation can be
 done programatically, which is what this category allows you to do.
 */
@interface RKObjectMapping (TransformationMapping)

/* Adds attribute mappings for the given source keys, applying the transformation
 block to each source key in turn to derive the destination attribute key.
 
 Simply pass in a block, and within that block, apply whatever string transformation
 makes sense to the provided source key and return a destination key.
 
 If your block returns nil, the key will be skipped.
 */
- (void)addAttributeMappingsFromArrayOfSourceKeys:(NSArray *)keys
   transformSourceKeysToDestinationKeysUsingBlock:(RKObjectMappingSourceKeyTransformationBlock)block;

@end

RKObjectMapping+TransformationMapping.m

//
//  RKObjectMapping+TransformationMapping.m
//  OtherScreen
//
//  Created by Luke Redpath on 05/10/2012.
//

#import "RKObjectMapping+TransformationMapping.h"

@implementation RKObjectMapping (TransformationMapping)

- (void)addAttributeMappingsFromArrayOfSourceKeys:(NSArray *)keys
   transformSourceKeysToDestinationKeysUsingBlock:(RKObjectMappingSourceKeyTransformationBlock)block
{
  NSMutableDictionary *mappings = [NSMutableDictionary dictionaryWithCapacity:keys.count];
  
  [keys enumerateObjectsUsingBlock:^(id sourceKey, NSUInteger idx, BOOL *stop) {
    NSString *destinationKey = block(sourceKey);
    
    if (destinationKey) {
      [mappings setObject:destinationKey forKey:sourceKey];
    }
  }];
  
  [self addAttributeMappingsFromDictionary:mappings];
}

@end