使用云函数时，firestore中的时间戳将转换为地图
使用云函数时，firestore中的时间戳将转换为地图
提问于 2019-05-22 03:24:57
因此，我在云firestore中有一个Timestamp。我正在使用云函数从firestore到flutter检索数据。但是JSON格式化时间戳到映射，由于这我不能使用它作为时间戳。如何将其再次转换为时间戳？
这就是我将时间戳放到firestore的方法。
var reference = Firestore.instance.collection('posts');
reference.add({
'postTitle': this.title,
'timestamp': DateTime.now(),
'likes': {},
'ownerId': userId,
})要检索数据，代码如下：
factory Post.fromJSON(Map data){
return Post(
timestamp: data['timestamp'],
);
}List<Post> _generateFeed(List<Map<String, dynamic>> feedData) {
List<Post> listOfPosts = [];
for (var postData in feedData) {
listOfPosts.add(Post.fromJSON(postData));
}
return listOfPosts;
}但是这会返回一个错误。
I/flutter (17271): The following assertion was thrown building FutureBuilder<DocumentSnapshot>(dirty, state:
I/flutter (17271): _FutureBuilderState<DocumentSnapshot>#1536b):
I/flutter (17271): type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Timestamp'这是我的云函数。
getFeed.ts
import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
export const getFeedModule = function(req, res){
const uid = String(req.query.uid);
async function compileFeedPost(){
const following = await getFollowing(uid, res)as any;
let listOfPosts = await getAllPosts(following, res);
listOfPosts = [].concat.apply([], listOfPosts);
res.send(listOfPosts);
}
compileFeedPost().then().catch();
}
async function getAllPosts(following, res) {
let listOfPosts = [];
for (let user in following){
listOfPosts.push( await getUserPosts(following[user], res));
}
return listOfPosts;
}
function getUserPosts(userId, res){
const posts = admin.firestore().collection("posts").where("ownerId", "==", userId).orderBy("timestamp")
return posts.get()
.then(function(querySnapshot){
let listOfPosts = [];
querySnapshot.forEach(function(doc){
listOfPosts.push(doc.data());
});
return listOfPosts;
})
}
function getFollowing(uid, res){
const doc = admin.firestore().doc(`user/${uid}`)
return doc.get().then(snapshot => {
const followings = snapshot.data().followings;
let following_list = [];
for (const following in followings){
if (followings[following] === true){
following_list.push(following);
}
}
return following_list;
}).catch(error => {
res.status(500).send(error)
})
}云函数index.ts
import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
import { getFeedModule } from "./getFeed"
admin.initializeApp();
export const getFeed = functions.https.onRequest((req, res) => {
getFeedModule(req, res);
})由此调用
_getFeed() async {
print("Starting getFeed");
FirebaseUser user = await FirebaseAuth.instance.currentUser();
SharedPreferences prefs = await SharedPreferences.getInstance();
String userId = user.uid;
var url =
'https://us-central1-jaluk-quiz.cloudfunctions.net/getFeed?uid=' + userId;
var httpClient = HttpClient();
List<QuizViewer>listOfPosts;
String result;
try {
var request = await httpClient.getUrl(Uri.parse(url));
var response = await request.close();
if (response.statusCode == HttpStatus.ok) {
String json = await response.transform(utf8.decoder).join();
prefs.setString("feed", json);
List<Map<String, dynamic>> data =
jsonDecode(json).cast<Map<String, dynamic>>();
listOfPosts = _generateFeed(data);
result = "Success in http request for feed";
} else {
result =
'Error getting a feed: Http status ${response.statusCode} | userId $userId';
}
} catch (exception) {
result = 'Failed invoking the getFeed function. Exception: $exception';
}
print(result);
setState(() {
feedData = listOfPosts;
});
}回答 7
Stack Overflow用户
回答已采纳
发布于 2019-05-22 06:16:47
如果您正在处理的时间戳已被序列化为具有秒和纳秒组件的对象，则可以使用这些组件通过new Timestamp(seconds, nanoseconds)创建新的Timestamp对象。
Stack Overflow用户
发布于 2019-09-10 14:38:53
事实上，在使用云函数时，时间戳会以普通地图的形式返回。但是如果你使用Firebase SDK，它会返回Timestamp对象。我使用以下函数来处理这两种情况：
/// https://stackoverflow.com/a/57865272/1321917
DateTime dateTimeFromTimestamp(dynamic val) {
Timestamp timestamp;
if (val is Timestamp) {
timestamp = val;
} else if (val is Map) {
timestamp = Timestamp(val['_seconds'], val['_nanoseconds']);
}
if (timestamp != null) {
return timestamp.toDate();
} else {
print('Unable to parse Timestamp from $val');
return null;
}
}与json_annotation库完美配合：
@JsonKey(
fromJson: dateTimeFromTimestamp,
toJson: dateTimeToTimestamp,
nullable: true)
final DateTime subscriptionExpiryDate;Stack Overflow用户
发布于 2021-03-26 23:02:29
您可以使用converted接收DateTime，如下所示：
class TimestampConverter implements JsonConverter<DateTime, dynamic> {
const TimestampConverter();
@override
DateTime fromJson(dynamic data) {
Timestamp timestamp;
if (data is Timestamp) {
timestamp = data;
} else if (data is Map) {
timestamp = Timestamp(data['_seconds'], data['_nanoseconds']);
}
return timestamp?.toDate();
}
@override
Map<String, dynamic> toJson(DateTime dateTime) {
final timestamp = Timestamp.fromDate(dateTime);
return {
'_seconds': timestamp.seconds,
'_nanoseconds': timestamp.nanoseconds,
};
}
}然后像这样标记你的模型字段：
@TimestampConverter() DateTime createdAt页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/56245156
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