当我使用 addSnapshotListener 进行实时更新时，文档会重复，但情况并非如此，但是当使用 getDocuments() 时，文档只重复一次，我需要使用 addSnaphotListener 但不想重复文档读取，请协助我使用快照监听器的错误。
我在 Swift iOS 中使用 Firestore 数据库。下面是我正在使用的代码
带有 addSnapShotListener() 的代码:
func getComments() {
//print(postId + "received")
let commentsRef = Firestore.firestore().collection("posts").document(postId).collection("comments")
commentsRef.addSnapshotListener { (snapshot, error) in
if let error = error {
print(error.localizedDescription)
} else {
if let snapshot = snapshot {
for document in snapshot.documents {
// self.length = snapshot.count
let data = document.data()
let username = data["comment_author_username"] as? String ?? ""
let comment = data["comment_author_comment"] as? String ?? ""
let spinnerC = data["comment_author_spinnerC"] as? String ?? ""
let fullname = data["comment_author_fullname"] as? String ?? ""
let email = data["comment_author_email"] as? String ?? ""
let commentUserImageUrl = data["comment_user_image"] as? String ?? ""
let commentuser_id = data["comment_author_id"] as? String ?? ""
self.checkl1value = data["l1"] as? Bool
let newComment = Comment(_documentId: document.documentID, _commentAuthorUsername: username, _commentAuthorFullName: fullname, _commentAuthorComment: comment, _commentUserImage: commentUserImageUrl, _commentAuthorSpinnerC: spinnerC, _commentAuthorId:commentuser_id, _checkl1value: self.checkl1value)
self.comments.append(newComment)
// print(self.length!)
}
self.tableView.reloadData()
}
}
}
}
使用 getDocuments() 编写代码:
func getComments() {
//print(postId + "received")
let commentsRef = Firestore.firestore().collection("posts").document(postId).collection("comments")
commentsRef.getDocuments { (snapshot, error) in
if let error = error {
print(error.localizedDescription)
} else {
if let snapshot = snapshot {
for document in snapshot.documents {
// self.length = snapshot.count
let data = document.data()
let username = data["comment_author_username"] as? String ?? ""
let comment = data["comment_author_comment"] as? String ?? ""
let spinnerC = data["comment_author_spinnerC"] as? String ?? ""
let fullname = data["comment_author_fullname"] as? String ?? ""
let email = data["comment_author_email"] as? String ?? ""
let commentUserImageUrl = data["comment_user_image"] as? String ?? ""
let commentuser_id = data["comment_author_id"] as? String ?? ""
self.checkl1value = data["l1"] as? Bool
let newComment = Comment(_documentId: document.documentID, _commentAuthorUsername: username, _commentAuthorFullName: fullname, _commentAuthorComment: comment, _commentUserImage: commentUserImageUrl, _commentAuthorSpinnerC: spinnerC, _commentAuthorId:commentuser_id, _checkl1value: self.checkl1value)
self.comments.append(newComment)
// print(self.length!)
}
self.tableView.reloadData()
}
}
}
}
最佳答案
您可能只想处理快照之间的更改。为此，您需要遍历 而不是 ，如 viewing changes between snapshots 上的文档所示。 :
db.collection("cities").whereField("state", isEqualTo: "CA") .addSnapshotListener { querySnapshot, error in guard let snapshot = querySnapshot else { print("Error fetching snapshots: \(error!)") return } snapshot.documentChanges.forEach { diff in if (diff.type == .added) { print("New city: \(diff.document.data())") } if (diff.type == .modified) { print("Modified city: \(diff.document.data())") } if (diff.type == .removed) { print("Removed city: \(diff.document.data())") } } }
最初，您的监听器将通过 diff.type == .added 为每个现有文档调用，然后当有更改时，它将通过 type< 的正确组合调用s.
关于ios - AddSnapShotListener 在一个实例中重复读取文档，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/58967357/