我正在尝试从 firebase 获取所有当前用户未读的消息。问题是我的 onSnapshot() 返回以下错误，但它在初始加载时返回我所需的值。如果添加了新文档，则 onSnapshot( ) 不会因为该错误而再次触发
这是接收所有当前用户未读消息的辅助函数。
async getUnseenMessagesCount() {
const collectionRef = (await firestore()).collection(this.collectionPath) //chats/${user_id+second_identifier/messages}
let allMessagesCount = 0
let currentUserReadMessagesCount = 0
try {
collectionRef.onSnapshot().then(snapshot => {
allMessagesCount = snapshot.docs.length
})
collectionRef
.where('seenBy', '==', '') // compare against empty string because seenBy is userId.
.onSnapshot()
.then(snapshot => {
currentUserReadMessagesCount = snapshot.docs.length
})
} catch (error) {
console.log(error)
}
console.log(allMessagesCount)
console.log(currentUserReadMessagesCount)
console.log(allMessagesCount - currentUserReadMessagesCount)
}
由于我想从用户参与的所有聊天中获取所有未读消息计数，因此我在我的 vuex 操作中执行以下操作，该操作在身份验证状态更改时激活:
new UserChatsDB(newUser.id).readAll().then(snapshot => { //users/id/chats/{chat_id: user_id+second_identifier}
if (snapshot.length > 0) {
snapshot.forEach(element => {
console.log(element)
const count = new MessagesDB(
element.chat_id
).getUnseenMessagesCount()
console.log(count) //Returns pending Promise
})
}
})
什么会导致上述错误？有没有更好的方法来解决这个问题？让我知道是否需要数据库结构。任何帮助深表感谢!如果可以在 firebase 上使用套接字，或者如果推送通知可以在每个设备上工作，一切都会容易得多。
最佳答案
根据firebase的docs，你必须像这样使用onSnapshot()函数:
async getUnseenMessagesCount() {
const collectionRef = (await firestore()).collection(this.collectionPath) //chats/${user_id+second_identifier/messages}
let allMessagesCount = 0
let currentUserReadMessagesCount = 0
try {
collectionRef.onSnapshot(snapshot => {
allMessagesCount = snapshot.docs.length
})
collectionRef
.where('seenBy', '==', '') // compare against empty string because seenBy is userId.
.onSnapshot(snapshot => {
currentUserReadMessagesCount = snapshot.docs.length
})
} catch (error) {
console.log(error)
}
console.log(allMessagesCount)
console.log(currentUserReadMessagesCount)
console.log(allMessagesCount - currentUserReadMessagesCount)
}
所以你必须删除你的
then() 。关于javascript - Firestore 抛出 'onSnapshot() requires between 1 and 4 arguments'，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/57903018/