IOS NSDictionary with json

#import <Foundation/Foundation.h>

@interface NSDictionary(JSONCategories)
+(NSDictionary*)dictionaryWithContentsOfJSONURLString:(NSString*)urlAddress;
-(NSData*)toJSON;
+(NSDictionary*)dictionaryWithContentsOfJSONFromString:(NSString*) jsonString;
@end
 ////////////////////////////////////////////////////////////////////////////////////////////////////////
#import "NSDictionaryJSON.h"
@implementation NSDictionary(JSONCategories)
+(NSDictionary*)dictionaryWithContentsOfJSONURLString:(NSString*)urlAddress {
    NSData* data = [NSData dataWithContentsOfURL: [NSURL URLWithString: urlAddress] ];
    __autoreleasing NSError* error = nil;
    @try {
        id result = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
        if (error != nil) return nil;
        return result;
    }
    @catch (NSException *exception) {
        NSLog(@"Error file");
    }
    return nil;
}

+(NSDictionary*)dictionaryWithContentsOfJSONFromString:(NSString*) jsonString {
    NSData* data = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
    __autoreleasing NSError* error = nil;
    id result = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
    if (error != nil) return nil;
    return result;
}

-(NSData*)toJSON {
    NSError* error = nil;
    id result = [NSJSONSerialization dataWithJSONObject:self options:kNilOptions error:&error];
    if (error != nil) return nil;
    return result;
}
@end