A category for retrieving objects from nested NSDictionaries

NSDictionary+JBSObjectForPath.h

#import <Foundation/Foundation.h>

@interface NSDictionary (JBSObjectForPath)
/**
 Returns the object from a nested `NSDictionary` at the given path, with path
 components separated by a "/". For example, if you have the following 
 dictionary:
 
 ~~~~
 {"foo":{"bar":"foobar"}}
 ~~~~
 
 Then the path `@"foo/bar"` would return the `NSString` `@"foobar"`.
 
 @param path A string path with compenents separated by a "/".
 
 @return The object at the specified path.
 */
- (id)objectForKeyPath:(NSString *)path;

/**
 @see objectForKeyPath:
 
 @param path A string path with components separated by the specified separator.
 @param separator A string that defines the components separator.
 
 @return The object at the specified path.
 */
- (id)objectForKeyPath:(NSString *)path withPathSeparator:(NSString *)separator;
@end

NSDictionary+JBSObjectForPath.m

#import "NSDictionary+JBSObjectForPath.h"

@implementation NSDictionary (JBSObjectForPath)
- (id)objectForKeyPath:(NSString *)path
{
  return [self objectForKeyPath:path withPathSeparator:@"/"];
}

- (id)objectForKeyPath:(NSString *)path withPathSeparator:(NSString *)separator
{
  NSCharacterSet *cset = [NSCharacterSet
                          characterSetWithCharactersInString:separator];
  if (!path || [path rangeOfCharacterFromSet:cset].location == NSNotFound) {
    return nil;
  }
  
  NSArray *keys = [path componentsSeparatedByString:separator];
  
  __block id (^getObject)();
  getObject = ^id(NSArray *keypath, NSDictionary *dict) {
    if ([keypath count] == 1) {
      return [dict objectForKey:[keypath objectAtIndex:0]];
    }
    
    NSRange range;
    range.location = 1;
    range.length = [keypath count] - 1;
    NSArray *ar = [keypath subarrayWithRange:range];
    return getObject(ar, [dict objectForKey:[keypath objectAtIndex:0]]);
  };
  
  return getObject(keys, self);
}
@end