1.字典

NSMutableDictionary *dicFriends = [[NSMutableDictionary alloc] init];

[dicFriends setObject:friends forKey:@"usernames"];

NSData *dataFriends = [NSJSONSerialization dataWithJSONObject:dicFriends options:NSJSONWritingPrettyPrinted error:nil];

NSString *jsonString = [[NSString alloc] initWithData:dataFriends

encoding:NSUTF8StringEncoding];

（ps? usernames 是字段，jsonString是轉(zhuǎn)換json格式的字典）

2.數(shù)組

數(shù)組其實(shí)和字典一樣，只需將（dataWithJSONObject：dicFriends）參數(shù)，換成數(shù)組就可以了