Question

当我使用addSnapshotListener进行实时更新时，文件会被重复，但情况并非如此，但是当使用getDocuments()时，文件仅被重复一次，我需要使用addSnaphotListener但不希望要复制文档阅读，请在使用快照侦听器时出现错误的地方提供帮助。

我正在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()
                }
            }
        }
    }

带有getDocuments()的代码：

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()
                }
            }
        }
    }

Answer 1

您可能只想处理快照之间的更改。为此，您需要遍历instead of，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，将为每个现有文档使用diff.type == .added调用您的侦听器，然后当发生更改时，将使用type s的正确混合来调用它。

AddSnapShotListener在一个实例中重复读取文档

1 个答案: