ios开发数组对象怎么转换成json 然后在转为字符串

数组换JSon字符串
NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
[dictionary setValue:@"hello" forKey:@"one"];
[dictionary setValue:@"world" forKey:@"two"];
NSArray *arry=[NSArray arrayWithObjects:@"001",@"002",@"003", nil];
[dictionary setValue:arry forKey:@"three"];
NSData *data=[NSJSONSerialization dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:nil];
NSString *jsonStr=[[NSString alloc]initWithData:dataencoding:NSUTF8StringEncoding];
NSLog(@"jsonStr==%@",jsonStr);