自动推送新聊天信息并更新Firebase实时数据库上的lastMessage值
我将聊天信息和聊天元数据存储在此结构中:自动推送新聊天信息并更新Firebase实时数据库上的lastMessage值,firebase,firebase-realtime-database,transactions,atomic,Firebase,Firebase Realtime Database,Transactions,Atomic,我将聊天信息和聊天元数据存储在此结构中: project | -- chats | -- 1 | -- -MFBvnTIQgVKdyFzDMpy | -- message: "hello" | -- -MEZutiaxOthE-7nDOkA | -- message: "how are you?" | -- 2
project
|
-- chats
|
-- 1
|
-- -MFBvnTIQgVKdyFzDMpy
|
-- message: "hello"
|
-- -MEZutiaxOthE-7nDOkA
|
-- message: "how are you?"
|
-- 2
|
-- -MENuu8TjwWrBTkIzue_
|
-- message: "hi"
|
-- -MFBTqEqhR9Dtv3MlMd6
|
-- message: "you good?"
|
-- chatMetadata
|
-- 1
|
-- lastMessage: "how are you?"
|
-- 2
|
-- lastMessage: "you good?"
每当用户向特定聊天室提交新的聊天信息时,该聊天室的lastMessage属性应在chatMetadata中更新。该过程包含两个单独的操作:
.push()
用于推送新的聊天信息,以及.update()
用于更新lastMessage属性。如果多个用户可以同时向特定聊天室提交消息,我如何保证lastMessage始终等于last pushed chat message?云功能必须使用实时数据库触发器才能做到这一点
// Listens for new messages added to /chats/:chatId/ and creates an
// uppercase version of the message to /chatMetadata/:chatId/
exports.updateLastMessage = functions.database.ref('/chats/{chatId}/')
.onCreate((snapshot, context) => {
// Grab the current value of what was written to the Realtime Database.
const original = snapshot.val();
// You must return a Promise when performing asynchronous tasks inside a Functions
// Writing the lastMessage node
return snapshot.ref.parent.parent.child('chatMetadata').child(context.params.chatId).set({lastMessage: original.message});
});