NSJSONSerialization 组json字符串

抄的网上的. 主要是组织列表部分

    NSDictionary *song = [NSDictionary dictionaryWithObjectsAndKeys:@"i can fly",@"title",@"",@"length",@"Tom",@"Singer", nil];
    NSMutableDictionary *data1 = [[NSMutableDictionary alloc] initWithDictionary:song];
    NSMutableArray *list = [[NSMutableArray alloc] init];
    for (int i=; i<; i++) {
        [list addObject:song];
    }
    [data1 setValue:list forKey:@"data1"];

    if ([NSJSONSerialization isValidJSONObject:data1])
    {
        NSError *error;
        NSData *jsonData = [NSJSONSerialization dataWithJSONObject:data1 options:NSJSONWritingPrettyPrinted error:&error];
        NSString *json =[[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
        NSLog(@"json data:%@",json);
    }