[英]Listening to one added document in Firestore - Swift
I'm listening to only one added document in a collection, and after it is read I need this document to be deleted.我只听一个集合中添加的文档,阅读后我需要删除该文档。 This is the code I implemented:这是我实现的代码:
func createListener(){
guard let currentUid = Auth.auth().currentUser?.uid else { return }
listener = db.collection("Collection").document(currentUid).collection("Collection").addSnapshotListener({ listenerSnapshot, error in
if let error = error{
print(error.localizedDescription)
return
}
listenerSnapshot?.documentChanges.forEach({ change in
if change.type == .added{
let data = change.document.data()
let myview = MYView(data: data)
guard let window = UIApplication.shared.windows.last else { return }
myview.present(to: window) {
change.document.reference.delete()
}
}
})
})
}
The problem is that after the document is deleted with问题是文件被删除后
change.document.reference.delete()更改.document.reference.delete()
The listener snippet change.type ==.added
is triggered even if the document has been deleted.即使文档已被删除,侦听器片段change.type ==.added
也会被触发。 I don't know why...我不知道为什么...
How can I only listen for actually ADDED documents in a Firestore Collection?我如何才能只收听 Firestore 集合中实际添加的文档?
EDIT:编辑:
listening for a specific document but still closure called when document is deleted:侦听特定文档但在删除文档时仍调用闭包:
listener = db.collection("Collection").document(currentUid).addSnapshotListener({ listenerSnapshot, error in
if let error = error{
print(error.localizedDescription)
return
}
guard let data = listenerSnapshot?.data() else { return }
let myview = MYView(data: data)
guard let window = UIApplication.shared.windows.last else { return }
myview.present(to: window) {
listenerSnapshot?.reference.delete()
}
})
I'm listening to only one added document in a collection.我只听了一个集合中添加的文档。
No, you're not.不你不是。 You're attaching a snapshot listener to a collection and not to a single document:您将快照侦听器附加到集合而不是单个文档:
db.collection("Collection")
.document(currentUid)
.collection("Collection") //👈
.addSnapshotListener(/* ... */)
This means that you're listening for real-time updates for each operation that takes place inside the entire sub-collection called "Collection".这意味着您正在侦听在称为“集合”的整个子集合中发生的每个操作的实时更新。
What you're basically doing, you're saying, hey Firestore, give me all documents that exist in that sub-collection and keep the listener alive.你基本上在做什么,你在说,嘿 Firestore,给我那个子集合中存在的所有文档,让听众保持活力。 This listener will be invoked every time a document in that collection changes over time.每当该集合中的文档随时间发生变化时,都会调用此侦听器。
If you want to listen to a single document, then you should add a call to .document()
and pass a specific document ID:如果您想收听单个文档,则应添加对.document()
的调用并传递特定的文档 ID:
db.collection("Collection")
.document(currentUid)
.collection("Collection")
.document("someDocumentId") //👈
.addSnapshotListener(/* ... */)
In this way, you'll only be notified about the changes to a single document.这样,您只会收到有关单个文档更改的通知。
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