iOS对象（字典或数组）转化为JSon字符串

 NSMutableDictionary*dictionary = [[NSMutableDictionaryalloc]init];

    [dictionary setValue:@"hello" forKey:@"one"];

    [dictionary setValue:@"world" forKey:@"two"];

   NSArray*arry=[NSArrayarrayWithObjects:@"001",@"002",@"003",nil];

    [dictionary setValue:arry forKey:@"three"];

   NSData*data=[NSJSONSerializationdataWithJSONObject:dictionaryoptions:NSJSONWritingPrettyPrintederror:nil];

   NSString*jsonStr=[[NSStringalloc]initWithData:dataencoding:NSUTF8StringEncoding];

    NSLog(@"jsonStr==%@",jsonStr);

输出结果为：

str=={

  "one" : "hello",

  "two" : "world",

  "three" : [

    "001",

    "002",

    "003"

  ]

}