序列化失败 JSON Objective-c
Fail to serialize JSON Objective-c
我有问题。当我尝试 make test my json 时，它说它无效。但是当我用在线服务测试它时，它读起来很好。
我用来测试json是否有效的代码是：
NSString* stringRes = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
[NSJSONSerialization isValidJSONObject:stringRes];
其中stringRes是NSString格式的子字符串。（来自数据响应）
JSON :
{
"response": [
9,
{
"id": 47,
"from_id": 211551056,
"to_id": -101815039,
"date": 1442585775,
"post_type": "post",
"text": "Кто на андроид кодит хоть немножк ? Хотя бы hello world ?",
"can_edit": 1,
"created_by": 211551056,
"can_delete": 1,
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 0,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
},
{
"id": 43,
"from_id": 217702824,
"to_id": -101815039,
"date": 1442555658,
"post_type": "post",
"text": "Учебник по географии",
"can_delete": 1,
"attachment": {
"type": "doc",
"doc": {
"did": 419802605,
"owner_id": 217702824,
"title": "11_geo_m_2012.pdf",
"size": 92318316,
"ext": "pdf",
"url": "http://vk.com/doc217702824_419802605?hash=5eb9bb9753a6f88e88&dl=fcadca27db5845a002&api=1",
"access_key": "8e4218746055687cc2"
}
},
"attachments": [
{
"type": "doc",
"doc": {
"did": 419802605,
"owner_id": 217702824,
"title": "11_geo_m_2012.pdf",
"size": 92318316,
"ext": "pdf",
"url": "http://vk.com/doc217702824_419802605?hash=5eb9bb9753a6f88e88&dl=fcadca27db5845a002&api=1",
"access_key": "8e4218746055687cc2"
}
}
],
"post_source": {
"type": "api",
"platform": "android"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 3,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 0,
"reply_count": 0
},
{
"id": 37,
"from_id": 211551056,
"to_id": -101815039,
"date": 1442502437,
"post_type": "post",
"text": "У кого айфон, + в комменты",
"can_delete": 1,
"attachment": {
"type": "poll",
"poll": {
"poll_id": 195892301,
"question": "Удобно смотреть расписание ?(На сайте)"
}
},
"attachments": [
{
"type": "poll",
"poll": {
"poll_id": 195892301,
"question": "Удобно смотреть расписание ?(На сайте)"
}
}
],
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 5,
"can_post": 1
},
"likes": {
"count": 0,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 5
},
{
"id": 36,
"from_id": 249011483,
"to_id": -101815039,
"date": 1442500757,
"post_type": "post",
"text": "Домашку выложить не забудьте ",
"can_delete": 1,
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 1,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
},
{
"id": 28,
"from_id": 211551056,
"to_id": -101815039,
"date": 1442306249,
"post_type": "post",
"text": "",
"can_delete": 1,
"media": {
"type": "photo",
"owner_id": -101815039,
"item_id": 381477357,
"thumb_src": "http://cs624425.vk.me/v624425056/49e35/_w_YDirrrQU.jpg"
},
"attachment": {
"type": "photo",
"photo": {
"pid": 381477357,
"aid": -8,
"owner_id": -101815039,
"user_id": 211551056,
"src": "http://cs624425.vk.me/v624425056/49e35/_w_YDirrrQU.jpg",
"src_big": "http://cs624425.vk.me/v624425056/49e36/439edT8aXks.jpg",
"src_small": "http://cs624425.vk.me/v624425056/49e34/uLxZj9yF1F4.jpg",
"src_xbig": "http://cs624425.vk.me/v624425056/49e37/nhvaG43cV-Y.jpg",
"src_xxbig": "http://cs624425.vk.me/v624425056/49e38/Ox54xM039hg.jpg",
"width": 960,
"height": 720,
"text": "",
"created": 1442306250,
"lat": 55.785025,
"long": 37.706605,
"post_id": 28,
"access_key": "454823aa95a2ee9fbc"
}
},
"attachments": [
{
"type": "photo",
"photo": {
"pid": 381477357,
"aid": -8,
"owner_id": -101815039,
"user_id": 211551056,
"src": "http://cs624425.vk.me/v624425056/49e35/_w_YDirrrQU.jpg",
"src_big": "http://cs624425.vk.me/v624425056/49e36/439edT8aXks.jpg",
"src_small": "http://cs624425.vk.me/v624425056/49e34/uLxZj9yF1F4.jpg",
"src_xbig": "http://cs624425.vk.me/v624425056/49e37/nhvaG43cV-Y.jpg",
"src_xxbig": "http://cs624425.vk.me/v624425056/49e38/Ox54xM039hg.jpg",
"width": 960,
"height": 720,
"text": "",
"created": 1442306250,
"lat": 55.785025,
"long": 37.706605,
"post_id": 28,
"access_key": "454823aa95a2ee9fbc"
}
}
],
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 1,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
},
{
"id": 27,
"from_id": 211551056,
"to_id": -101815039,
"date": 1442306164,
"post_type": "post",
"text": "",
"can_delete": 1,
"media": {
"type": "photo",
"owner_id": -101815039,
"item_id": 381477244,
"thumb_src": "http://cs624425.vk.me/v624425056/49e2c/kttj5pUpjTk.jpg"
},
"attachment": {
"type": "photo",
"photo": {
"pid": 381477244,
"aid": -8,
"owner_id": -101815039,
"user_id": 211551056,
"src": "http://cs624425.vk.me/v624425056/49e2c/kttj5pUpjTk.jpg",
"src_big": "http://cs624425.vk.me/v624425056/49e2d/ihg9szTvLew.jpg",
"src_small": "http://cs624425.vk.me/v624425056/49e2b/GpS0xwCa66c.jpg",
"src_xbig": "http://cs624425.vk.me/v624425056/49e2e/pe4tflJokqs.jpg",
"src_xxbig": "http://cs624425.vk.me/v624425056/49e2f/7vkU8nUyNxc.jpg",
"width": 960,
"height": 720,
"text": "",
"created": 1442306166,
"lat": 55.785083,
"long": 37.711116,
"post_id": 27,
"access_key": "cb01ac011f4abbc0af"
}
},
"attachments": [
{
"type": "photo",
"photo": {
"pid": 381477244,
"aid": -8,
"owner_id": -101815039,
"user_id": 211551056,
"src": "http://cs624425.vk.me/v624425056/49e2c/kttj5pUpjTk.jpg",
"src_big": "http://cs624425.vk.me/v624425056/49e2d/ihg9szTvLew.jpg",
"src_small": "http://cs624425.vk.me/v624425056/49e2b/GpS0xwCa66c.jpg",
"src_xbig": "http://cs624425.vk.me/v624425056/49e2e/pe4tflJokqs.jpg",
"src_xxbig": "http://cs624425.vk.me/v624425056/49e2f/7vkU8nUyNxc.jpg",
"width": 960,
"height": 720,
"text": "",
"created": 1442306166,
"lat": 55.785083,
"long": 37.711116,
"post_id": 27,
"access_key": "cb01ac011f4abbc0af"
}
}
],
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 1,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
},
{
"id": 16,
"from_id": 249011483,
"to_id": -101815039,
"date": 1442069345,
"post_type": "post",
"text": "Кто нибудь сделал алгебру ?",
"can_delete": 1,
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 6,
"can_post": 1
},
"likes": {
"count": 3,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 6
},
{
"id": 9,
"from_id": 127082413,
"to_id": -101815039,
"date": 1441911418,
"post_type": "post",
"text": "Официальная информациия ,староста нашей группы Александр Кондор!",
"can_delete": 1,
"post_source": {
"type": "api",
"platform": "android"
},
"comments": {
"count": 6,
"can_post": 1
},
"likes": {
"count": 2,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 6
},
{
"id": 1,
"from_id": -101815039,
"to_id": -101815039,
"date": 1441656588,
"post_type": "post",
"text": "",
"can_delete": 1,
"can_pin": 1,
"media": {
"type": "photo",
"owner_id": -101815039,
"item_id": 380592775,
"thumb_src": "http://cs629111.vk.me/v629111548/e99f/DcV1yHZK1fw.jpg"
},
"attachment": {
"type": "photo",
"photo": {
"pid": 380592775,
"aid": -6,
"owner_id": -101815039,
"user_id": 100,
"src": "http://cs629111.vk.me/v629111548/e99f/DcV1yHZK1fw.jpg",
"src_big": "http://cs629111.vk.me/v629111548/e9a0/Qf8q8PpH7Jg.jpg",
"src_small": "http://cs629111.vk.me/v629111548/e99e/2Jq8e-0SptQ.jpg",
"src_xbig": "http://cs629111.vk.me/v629111548/e9a1/Uha0MvOoVCU.jpg",
"src_xxbig": "http://cs629111.vk.me/v629111548/e9a2/v8hqUldA6Kk.jpg",
"width": 730,
"height": 1024,
"text": "",
"created": 1441656588,
"post_id": 1
}
},
"attachments": [
{
"type": "photo",
"photo": {
"pid": 380592775,
"aid": -6,
"owner_id": -101815039,
"user_id": 100,
"src": "http://cs629111.vk.me/v629111548/e99f/DcV1yHZK1fw.jpg",
"src_big": "http://cs629111.vk.me/v629111548/e9a0/Qf8q8PpH7Jg.jpg",
"src_small": "http://cs629111.vk.me/v629111548/e99e/2Jq8e-0SptQ.jpg",
"src_xbig": "http://cs629111.vk.me/v629111548/e9a1/Uha0MvOoVCU.jpg",
"src_xxbig": "http://cs629111.vk.me/v629111548/e9a2/v8hqUldA6Kk.jpg",
"width": 730,
"height": 1024,
"text": "",
"created": 1441656588,
"post_id": 1
}
}
],
"post_source": {
"type": "api",
"platform": "android",
"data": "profile_photo"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 0,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
}
]
}
UPD：使用
解决
NSData* data = [stringRes dataUsingEncoding:NSUTF8StringEncoding];
isValidJSONObject 测试 JSON 对象（NSDictionary 或 NSArray）是否可以成功转换为 JSON 数据。
它不用于测试 NSData 对象是否包含有效的 JSON 数据。要测试有效的 JSON 数据，您只需调用
[NSJSON序列化JSONObjectWithData:data ...]
并检查 return 值是否为零。
我有问题。当我尝试 make test my json 时，它说它无效。但是当我用在线服务测试它时，它读起来很好。
我用来测试json是否有效的代码是：
NSString* stringRes = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
[NSJSONSerialization isValidJSONObject:stringRes];
其中stringRes是NSString格式的子字符串。（来自数据响应） JSON :
{
"response": [
9,
{
"id": 47,
"from_id": 211551056,
"to_id": -101815039,
"date": 1442585775,
"post_type": "post",
"text": "Кто на андроид кодит хоть немножк ? Хотя бы hello world ?",
"can_edit": 1,
"created_by": 211551056,
"can_delete": 1,
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 0,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
},
{
"id": 43,
"from_id": 217702824,
"to_id": -101815039,
"date": 1442555658,
"post_type": "post",
"text": "Учебник по географии",
"can_delete": 1,
"attachment": {
"type": "doc",
"doc": {
"did": 419802605,
"owner_id": 217702824,
"title": "11_geo_m_2012.pdf",
"size": 92318316,
"ext": "pdf",
"url": "http://vk.com/doc217702824_419802605?hash=5eb9bb9753a6f88e88&dl=fcadca27db5845a002&api=1",
"access_key": "8e4218746055687cc2"
}
},
"attachments": [
{
"type": "doc",
"doc": {
"did": 419802605,
"owner_id": 217702824,
"title": "11_geo_m_2012.pdf",
"size": 92318316,
"ext": "pdf",
"url": "http://vk.com/doc217702824_419802605?hash=5eb9bb9753a6f88e88&dl=fcadca27db5845a002&api=1",
"access_key": "8e4218746055687cc2"
}
}
],
"post_source": {
"type": "api",
"platform": "android"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 3,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 0,
"reply_count": 0
},
{
"id": 37,
"from_id": 211551056,
"to_id": -101815039,
"date": 1442502437,
"post_type": "post",
"text": "У кого айфон, + в комменты",
"can_delete": 1,
"attachment": {
"type": "poll",
"poll": {
"poll_id": 195892301,
"question": "Удобно смотреть расписание ?(На сайте)"
}
},
"attachments": [
{
"type": "poll",
"poll": {
"poll_id": 195892301,
"question": "Удобно смотреть расписание ?(На сайте)"
}
}
],
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 5,
"can_post": 1
},
"likes": {
"count": 0,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 5
},
{
"id": 36,
"from_id": 249011483,
"to_id": -101815039,
"date": 1442500757,
"post_type": "post",
"text": "Домашку выложить не забудьте ",
"can_delete": 1,
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 1,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
},
{
"id": 28,
"from_id": 211551056,
"to_id": -101815039,
"date": 1442306249,
"post_type": "post",
"text": "",
"can_delete": 1,
"media": {
"type": "photo",
"owner_id": -101815039,
"item_id": 381477357,
"thumb_src": "http://cs624425.vk.me/v624425056/49e35/_w_YDirrrQU.jpg"
},
"attachment": {
"type": "photo",
"photo": {
"pid": 381477357,
"aid": -8,
"owner_id": -101815039,
"user_id": 211551056,
"src": "http://cs624425.vk.me/v624425056/49e35/_w_YDirrrQU.jpg",
"src_big": "http://cs624425.vk.me/v624425056/49e36/439edT8aXks.jpg",
"src_small": "http://cs624425.vk.me/v624425056/49e34/uLxZj9yF1F4.jpg",
"src_xbig": "http://cs624425.vk.me/v624425056/49e37/nhvaG43cV-Y.jpg",
"src_xxbig": "http://cs624425.vk.me/v624425056/49e38/Ox54xM039hg.jpg",
"width": 960,
"height": 720,
"text": "",
"created": 1442306250,
"lat": 55.785025,
"long": 37.706605,
"post_id": 28,
"access_key": "454823aa95a2ee9fbc"
}
},
"attachments": [
{
"type": "photo",
"photo": {
"pid": 381477357,
"aid": -8,
"owner_id": -101815039,
"user_id": 211551056,
"src": "http://cs624425.vk.me/v624425056/49e35/_w_YDirrrQU.jpg",
"src_big": "http://cs624425.vk.me/v624425056/49e36/439edT8aXks.jpg",
"src_small": "http://cs624425.vk.me/v624425056/49e34/uLxZj9yF1F4.jpg",
"src_xbig": "http://cs624425.vk.me/v624425056/49e37/nhvaG43cV-Y.jpg",
"src_xxbig": "http://cs624425.vk.me/v624425056/49e38/Ox54xM039hg.jpg",
"width": 960,
"height": 720,
"text": "",
"created": 1442306250,
"lat": 55.785025,
"long": 37.706605,
"post_id": 28,
"access_key": "454823aa95a2ee9fbc"
}
}
],
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 1,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
},
{
"id": 27,
"from_id": 211551056,
"to_id": -101815039,
"date": 1442306164,
"post_type": "post",
"text": "",
"can_delete": 1,
"media": {
"type": "photo",
"owner_id": -101815039,
"item_id": 381477244,
"thumb_src": "http://cs624425.vk.me/v624425056/49e2c/kttj5pUpjTk.jpg"
},
"attachment": {
"type": "photo",
"photo": {
"pid": 381477244,
"aid": -8,
"owner_id": -101815039,
"user_id": 211551056,
"src": "http://cs624425.vk.me/v624425056/49e2c/kttj5pUpjTk.jpg",
"src_big": "http://cs624425.vk.me/v624425056/49e2d/ihg9szTvLew.jpg",
"src_small": "http://cs624425.vk.me/v624425056/49e2b/GpS0xwCa66c.jpg",
"src_xbig": "http://cs624425.vk.me/v624425056/49e2e/pe4tflJokqs.jpg",
"src_xxbig": "http://cs624425.vk.me/v624425056/49e2f/7vkU8nUyNxc.jpg",
"width": 960,
"height": 720,
"text": "",
"created": 1442306166,
"lat": 55.785083,
"long": 37.711116,
"post_id": 27,
"access_key": "cb01ac011f4abbc0af"
}
},
"attachments": [
{
"type": "photo",
"photo": {
"pid": 381477244,
"aid": -8,
"owner_id": -101815039,
"user_id": 211551056,
"src": "http://cs624425.vk.me/v624425056/49e2c/kttj5pUpjTk.jpg",
"src_big": "http://cs624425.vk.me/v624425056/49e2d/ihg9szTvLew.jpg",
"src_small": "http://cs624425.vk.me/v624425056/49e2b/GpS0xwCa66c.jpg",
"src_xbig": "http://cs624425.vk.me/v624425056/49e2e/pe4tflJokqs.jpg",
"src_xxbig": "http://cs624425.vk.me/v624425056/49e2f/7vkU8nUyNxc.jpg",
"width": 960,
"height": 720,
"text": "",
"created": 1442306166,
"lat": 55.785083,
"long": 37.711116,
"post_id": 27,
"access_key": "cb01ac011f4abbc0af"
}
}
],
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 1,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
},
{
"id": 16,
"from_id": 249011483,
"to_id": -101815039,
"date": 1442069345,
"post_type": "post",
"text": "Кто нибудь сделал алгебру ?",
"can_delete": 1,
"post_source": {
"type": "api",
"platform": "iphone"
},
"comments": {
"count": 6,
"can_post": 1
},
"likes": {
"count": 3,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 6
},
{
"id": 9,
"from_id": 127082413,
"to_id": -101815039,
"date": 1441911418,
"post_type": "post",
"text": "Официальная информациия ,староста нашей группы Александр Кондор!",
"can_delete": 1,
"post_source": {
"type": "api",
"platform": "android"
},
"comments": {
"count": 6,
"can_post": 1
},
"likes": {
"count": 2,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 6
},
{
"id": 1,
"from_id": -101815039,
"to_id": -101815039,
"date": 1441656588,
"post_type": "post",
"text": "",
"can_delete": 1,
"can_pin": 1,
"media": {
"type": "photo",
"owner_id": -101815039,
"item_id": 380592775,
"thumb_src": "http://cs629111.vk.me/v629111548/e99f/DcV1yHZK1fw.jpg"
},
"attachment": {
"type": "photo",
"photo": {
"pid": 380592775,
"aid": -6,
"owner_id": -101815039,
"user_id": 100,
"src": "http://cs629111.vk.me/v629111548/e99f/DcV1yHZK1fw.jpg",
"src_big": "http://cs629111.vk.me/v629111548/e9a0/Qf8q8PpH7Jg.jpg",
"src_small": "http://cs629111.vk.me/v629111548/e99e/2Jq8e-0SptQ.jpg",
"src_xbig": "http://cs629111.vk.me/v629111548/e9a1/Uha0MvOoVCU.jpg",
"src_xxbig": "http://cs629111.vk.me/v629111548/e9a2/v8hqUldA6Kk.jpg",
"width": 730,
"height": 1024,
"text": "",
"created": 1441656588,
"post_id": 1
}
},
"attachments": [
{
"type": "photo",
"photo": {
"pid": 380592775,
"aid": -6,
"owner_id": -101815039,
"user_id": 100,
"src": "http://cs629111.vk.me/v629111548/e99f/DcV1yHZK1fw.jpg",
"src_big": "http://cs629111.vk.me/v629111548/e9a0/Qf8q8PpH7Jg.jpg",
"src_small": "http://cs629111.vk.me/v629111548/e99e/2Jq8e-0SptQ.jpg",
"src_xbig": "http://cs629111.vk.me/v629111548/e9a1/Uha0MvOoVCU.jpg",
"src_xxbig": "http://cs629111.vk.me/v629111548/e9a2/v8hqUldA6Kk.jpg",
"width": 730,
"height": 1024,
"text": "",
"created": 1441656588,
"post_id": 1
}
}
],
"post_source": {
"type": "api",
"platform": "android",
"data": "profile_photo"
},
"comments": {
"count": 0,
"can_post": 1
},
"likes": {
"count": 0,
"user_likes": 0,
"can_like": 1,
"can_publish": 0
},
"reposts": {
"count": 0,
"user_reposted": 0
},
"online": 1,
"reply_count": 0
}
]
}
UPD：使用
解决NSData* data = [stringRes dataUsingEncoding:NSUTF8StringEncoding];
isValidJSONObject 测试 JSON 对象（NSDictionary 或 NSArray）是否可以成功转换为 JSON 数据。
它不用于测试 NSData 对象是否包含有效的 JSON 数据。要测试有效的 JSON 数据，您只需调用
[NSJSON序列化JSONObjectWithData:data ...]
并检查 return 值是否为零。