NSDictionary+Recursive.m

// find depth key in NSDictionary
- (id)findKey:(NSString *)keyname inObject:(id)object {
    
    for (id subKey in object) {
        
        id subObject = [object objectForKey:subKey];
        
        if ([subKey isEqualToString:keyname]) {
            return  subObject;
            
        } else if ([subObject isKindOfClass:[NSDictionary class]]) {
            
            return [self findKey:keyname inObject:subObject];
            
        } else if ([subObject isKindOfClass:[NSArray class]]) {
            
            return [self findKey:keyname inArray:subObject];
        }
        
    }
    
    return nil;
}

- (id)findKey:(NSString *)keyname inArray:(NSArray *)array {

    for (id sub in array) {
        if ([sub isKindOfClass:[NSDictionary class]]) {
            return [self findKey:keyname inObject:sub];
        } else if ([sub isKindOfClass:[NSArray class]]) {
            return [self findKey:keyname inObject:sub];
        }
    }
    
    return nil;
}