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[英]How to use Firestore realtime updates (onSnapshot) with redux-observable/rxjs?
[英]How to extract data when onSnapshot is returned in realtime firestore?
我有两个文件contact.js
和functions.js
。 我正在使用 Firestore 实时功能。
这是我的functions.js文件代码:
export const getUserContacts = () => {
const contactDetailsArr = [];
return db.collection("users").doc(userId)
.onSnapshot(docs => {
const contactsObject = docs.data().contacts;
for (let contact in contactsObject) {
db.collection("users").doc(contact).get()
.then(userDetail => {
contactDetailsArr.push({
userId: contact,
lastMessage: contactsObject[contact].lastMsg,
time: contactsObject[contact].lastMsgTime,
userName:userDetail.data().userName,
email: userDetail.data().emailId,
active: userDetail.data().active,
img: userDetail.data().imageUrl,
unreadMsg:contactsObject[contact].unreadMsg
})
})
}
console.log(contactDetailsArr);
return contactDetailsArr;
})
}
当我这样做时在contact.js
中:
useEffect(() => {
let temp = getUserContacts();
console.log(temp);
}, [])
我想在contacts.js
中提取contactDetailsArr
的数据,但我得到的 temp 值被控制台为:
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在我的情况下如何提取数组数据?
onSnapshot()
返回可用于分离 Firestore 侦听器的 function。 使用监听器时,最好将数据直接设置到 state 中,而不是从 function 中返回内容。 尝试重构代码,如下所示:
const [contacts, setContacts] = useState([]);
useEffect(() => {
const getUserContacts = () => {
const contactDetailsArr = [];
const detach = db.collection("users").doc(userId)
.onSnapshot(docs => {
const contactsObject = docs.data().contacts;
const contactsSnap = await Promise.all(contactsObject.map((c) => db.collection("users").doc(c).get()))
const contactDetails = contactsSnap.map((d) => ({
id: d.id,
...d.data()
// other fields like unreadMsg, time
}))
// Update in state
setContacts(contactDetails);
})
}
getUserContacts();
}, [])
然后使用contacts
数组将 map 数据直接输入到 UI。
此答案假设用户的数据在您的 Firestore 中如下所示:
// Document at /users/someUserId
{
"active": true,
"contacts": {
"someOtherUserId": {
"lastMsg": "This is a message",
"lastMsgTime": /* Timestamp */,
"unreadMsg": true // unclear if this is a boolean or a count of messages
},
"anotherUserId": {
"lastMsg": "Hi some user! How are you?",
"lastMsgTime": /* Timestamp */,
"unreadMsg": false
}
},
"emailId": "someuser@example.com",
"imageUrl": "https://firebasestorage.googleapis.com/b/bucket/o/images%20stars.jpg",
"userName": "Some User"
}
注:日后提问时,请添加与上述类似的数据结构示例
如上所示的结构有许多缺陷。 用户数据中的“联系人”object 应移动到用户主文档的子集合中。 其原因包括:
active
、 email
、 imageUrl
和userName
属性要在您的functions.js
库中获取用户的联系人一次,您可以使用:
// Utility function: Used to hydrate an entry in a user's "contacts" map
const getContactFromContactMapEntry = (db, [contactId, msgInfo]) => {
return db.collection("users")
.doc(contactId)
.get()
.then((contactDocSnapshot) => {
const { lastMsg, lastMsgTime, unreadMsg, userName } = msgInfo;
const baseContactData = {
lastMessage: lastMsg,
time: lastMsgTime,
unreadMsg,
userId: contactId
}
if (!contactDocSnapshot.exists) {
// TODO: Decide how to handle unknown/deleted users
return {
...baseContactData,
active: false, // deleted users are inactive, nor do they
email: null, // have an email, image or display name
img: null,
userName: "Deleted user"
};
}
const { active, emailId, imageUrl, userName } = contactDocSnapshot.data();
return {
...baseContactData,
active,
email: emailId,
img: imageUrl,
userName
};
});
};
export const getUserContacts = (db, userId) => { // <-- note that db and userId are passed in
return db.collection("users")
.doc(userId)
.get()
.then((userDataSnapshot) => {
const contactsMetadataMap = userDataSnapshot.get("contacts");
return Promise.all( // <-- waits for each Promise to complete
Object.entries(contactsMetadataMap) // <-- used to get an array of id-value pairs that we can iterate over
.map(getContactFromContactMapEntry.bind(null, db)); // for each contact, call the function (reusing db), returning a Promise with the data
);
});
}
示例用法:
getUserContacts(db, userId)
.then((contacts) => console.log("Contacts data:", contacts))
.catch((err) => console.error("Failed to get contacts:", err))
// OR
try {
const contacts = await getUserContacts(db, userId);
console.log("Contacts data:", contacts);
} catch (err) {
console.error("Failed to get contacts:", err)
}
要获取用户的联系人并保持列表更新,请在您的functions.js
库中使用 function,您可以使用:
// reuse getContactFromContactMapEntry as above
export const useUserContacts = (db, userId) => {
if (!db) throw new TypeError("Parameter 'db' is required");
const [userContactsData, setUserContactsData] = useState({ loading: true, contacts: [], error: null });
useEffect(() => {
// no user signed in?
if (!userId) {
setUserContactsData({ loading: false, contacts: [], error: "No user signed in" });
return;
}
// update loading status (as needed)
if (!userContactsData.loading) {
setUserContactsData({ loading: true, contacts: [], error: null });
}
let detached = false;
const detachListener = db.collection("users")
.doc(userId)
.onSnapshot({
next: (userDataSnapshot) => {
const contactsMetadataMap = userDataSnapshot.get("contacts");
const hydrateContactsPromise = Promise.all( // <-- waits for each Promise to complete
Object.entries(contactsMetadataMap) // <-- used to get an array of id-value pairs that we can iterate over
.map(getContactFromContactMapEntry.bind(null, db)); // for each contact, call the function (reusing db), returning a Promise with the data
);
hydrateContactsPromise
.then((contacts) => {
if (detached) return; // detached already, do nothing.
setUserContactsData({ loading: false, contacts, error: null });
})
.catch((err) => {
if (detached) return; // detached already, do nothing.
setUserContactsData({ loading: false, contacts: [], error: err });
});
},
error: (err) => {
setUserContactsData({ loading: false, contacts: [], error: err });
}
});
return () => {
detached = true;
detachListener();
}
}, [db, userId])
}
注意:上面的代码不会(由于复杂性):
setUserContactsData
方法被乱序调用时正确处理db
实例时处理示例用法:
const { loading, contacts, error } = useUserContacts(db, userId);
为了提高效率重组您的数据,您的结构将更新为以下内容:
// Document at /users/someUserId
{
"active": true,
"emailId": "someuser@example.com",
"imageUrl": "https://firebasestorage.googleapis.com/b/bucket/o/images%20stars.jpg",
"userName": "Some User"
}
// Document at /users/someUserId/contacts/someOtherUserId
{
"lastMsg": "This is a message",
"lastMsgTime": /* Timestamp */,
"unreadMsg": true // unclear if this is a boolean or a count of messages
}
// Document at /users/someUserId/contacts/anotherUserId
{
"lastMsg": "Hi some user! How are you?",
"lastMsgTime": /* Timestamp */,
"unreadMsg": false
}
使用上述结构提供以下好处:
要在您的functions.js
库中获取用户的联系人一次,您可以使用:
// Utility function: Merges the data from an entry in a user's "contacts" collection with that user's data
const mergeContactEntrySnapshotWithUserSnapshot = (contactEntryDocSnapshot, contactDocSnapshot) => {
const { lastMsg, lastMsgTime, unreadMsg } = contactEntryDocSnapshot.data();
const baseContactData = {
lastMessage: lastMsg,
time: lastMsgTime,
unreadMsg,
userId: contactEntryDocSnapshot.id
}
if (!contactDocSnapshot.exists) {
// TODO: Handle unknown/deleted users
return {
...baseContactData,
active: false, // deleted users are inactive, nor do they
email: null, // have an email, image or display name
img: null,
userName: "Deleted user"
};
}
const { active, emailId, imageUrl, userName } = contactDocSnapshot.data();
return {
...baseContactData,
active,
email: emailId,
img: imageUrl,
userName
};
}
// Utility function: Used to hydrate an entry in a user's "contacts" collection
const getContactFromContactsEntrySnapshot = (db, contactEntryDocSnapshot) => {
return db.collection("users")
.doc(contactEntry.userId)
.get()
.then((contactDocSnapshot) => mergeContactEntrySnapshotWithUserSnapshot(contactEntryDocSnapshot, contactDocSnapshot));
};
export const getUserContacts = (db, userId) => { // <-- note that db and userId are passed in
return db.collection("users")
.doc(userId)
.collection("contacts")
.get()
.then((userContactsQuerySnapshot) => {
return Promise.all( // <-- waits for each Promise to complete
userContactsQuerySnapshot.docs // <-- used to get an array of entry snapshots that we can iterate over
.map(getContactFromContactsEntrySnapshot.bind(null, db)); // for each contact, call the function (reusing db), returning a Promise with the data
);
});
}
示例用法:
getUserContacts(db, userId)
.then((contacts) => console.log("Contacts data:", contacts))
.catch((err) => console.error("Failed to get contacts:", err))
// OR
try {
const contacts = await getUserContacts(db, userId);
console.log("Contacts data:", contacts);
} catch (err) {
console.error("Failed to get contacts:", err)
}
为了以保持最新的方式获取用户的联系人,我们首先需要引入几个实用程序useEffect
包装器(有一些库可以实现更强大的实现):
export const useFirestoreDocument = ({ db, path }) => {
if (!db) throw new TypeError("Property 'db' is required");
const [documentInfo, setDocumentInfo] = useState({ loading: true, snapshot: null, error: null });
useEffect(() => {
if (!path) {
setDocumentInfo({ loading: false, snapshot: null, error: "Invalid path" });
return;
}
// update loading status (as needed)
if (!documentInfo.loading) {
setDocumentInfo({ loading: true, snapshot: null, error: null });
}
return db.doc(path)
.onSnapshot({
next: (docSnapshot) => {
setDocumentInfo({ loading: false, snapshot, error: null });
},
error: (err) => {
setDocumentInfo({ loading: false, snapshot: null, error: err });
}
});
}, [db, path]);
return documentInfo;
}
export const useFirestoreCollection = ({ db, path }) => {
if (!db) throw new TypeError("Property 'db' is required");
const [collectionInfo, setCollectionInfo] = useState({ loading: true, docs: null, error: null });
useEffect(() => {
if (!path) {
setCollectionInfo({ loading: false, docs: null, error: "Invalid path" });
return;
}
// update loading status (as needed)
if (!collectionInfo.loading) {
setCollectionInfo({ loading: true, docs: null, error: null });
}
return db.collection(path)
.onSnapshot({
next: (querySnapshot) => {
setCollectionInfo({ loading: false, docs: querySnapshot.docs, error: null });
},
error: (err) => {
setCollectionInfo({ loading: false, docs: null, error: err });
}
});
}, [db, path]);
return collectionInfo;
}
要使用该方法来水合联系人,您可以从ContactEntry
组件中调用它:
// mergeContactEntrySnapshotWithUserSnapshot is the same as above
const ContactEntry = ({ db, userId, key: contactId }) => {
if (!db) throw new TypeError("Property 'db' is required");
if (!userId) throw new TypeError("Property 'userId' is required");
if (!contactId) throw new TypeError("Property 'key' (the contact's user ID) is required");
const contactEntryInfo = useFirestoreDocument(db, `/users/${userId}/contacts/${contactId}`);
const contactUserInfo = useFirestoreDocument(db, `/users/${contactId}`);
if ((contactEntryInfo.loading && !contactEntryInfo.error) && (contactUserInfo.loading && !contactUserInfo.error)) {
return (<div>Loading...</div>);
}
const error = contactEntryInfo.error || contactUserInfo.error;
if (error) {
return (<div>Contact unavailable: {error.message}</div>);
}
const contact = mergeContactEntrySnapshotWithUserSnapshot(contactEntryInfo.snapshot, contactUserInfo.snapshot);
return (<!-- contact content here -->);
}
这些ContactEntry
组件将从Contacts
组件中填充:
const Contacts = ({db}) => {
if (!db) throw new TypeError("Property 'db' is required");
const { user } = useFirebaseAuth();
const contactsCollectionInfo = useFirestoreCollection(db, user ? `/users/${user.uid}/contacts` : null);
if (!user) {
return (<div>Not signed in!</div>);
}
if (contactsCollectionInfo.loading) {
return (<div>Loading contacts...</div>);
}
if (contactsCollectionInfo.error) {
return (<div>Contacts list unavailable: {contactsCollectionInfo.error.message}</div>);
}
const contactEntrySnapshots = contactsCollectionInfo.docs;
return (
<>{
contactEntrySnapshots.map(snapshot => {
return (<ContactEntry {...{ db, key: snapshot.id, userId: user.uid }} />);
})
}</>
);
}
示例用法:
const db = firebase.firestore();
return (<Contacts db={db} />);
您的代码似乎不是用 async/await 或 promise 之类的风格编写的
例如 contactDetailsArr 将作为空数组返回
onSnapshot 也会创建对 Firestore 集合的长期订阅,并且可以用简单的 get() 替换
请参阅Firestore https://firebase.google.com/docs/firestore/query-data/get-data#web-version-9_1上的示例
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