从检索Firebase中排除某些子项 [英] Exclude certain child from retrieving Firebase

问题描述

我希望检索某个集合中除一个特定子项之外的所有子项。我有由多个用户ID组成的数据库&USERS"；。

"users"
|- "userId1"
|- "userId2"
|- "userId3"

等等。 我现在只想检索"；userId1"；和"；userId3"；，并排除"；userId2"；。我已经知道如何只获取userId2，因为我还将其存储在另一个数据库中。该数据库由用户ID组成，构建如下：

"blocked-users"
|- "userId1" 
      |- "userId2"

这就是我要从检索用户中排除userId2的原因。假设userId1是CurrentUser，并且已经阻止了userId2，我想阻止userId1找到userId2。我该怎么做？

这就是我获取userId2的ID的方式：

guard let currentUid = Auth.auth().currentUser?.uid else { return }

BLOCKED_USERS.child(currentUid).observe(.childAdded) { (snapshot) in
                
    print("this is the user, that should not be shown: ", snapshot.key)

现在如何才能在此函数中排除Snapshot.key？：

var userCurrentKey: String?
USER_REF.queryLimited(toLast: 10).observeSingleEvent(of: .value) { (snapshot) in
                    
                    guard let first = snapshot.children.allObjects.first as? DataSnapshot else { return }
                    guard let allObjects = snapshot.children.allObjects as? [DataSnapshot] else { return }
                    
                    allObjects.forEach({ (snapshot) in
                        let uid = snapshot.key
                        
                        Database.fetchUser(with: uid, completion: { (user) in
                            self.users.append(user)
                            self.tableView.reloadData()
                        })
                    })
                    self.userCurrentKey = first.key
                }

这里是我为获取所有用户而调用的整个函数：

func fetchUsers() {
        
        guard let currentUid = Auth.auth().currentUser?.uid else { return }
        
        if userCurrentKey == nil {
            
            BLOCKED_USERS.child(currentUid).observe(.childAdded) { (snapshot) in
                print("these are the users that have blocked this user: ", snapshot.key)
                
                var dontShowThisUser = snapshot.key
                
                USER_REF.queryLimited(toLast: 10).observeSingleEvent(of: .value) { (snapshot) in
                    
                    guard let first = snapshot.children.allObjects.first as? DataSnapshot else { return }
                    guard let allObjects = snapshot.children.allObjects as? [DataSnapshot] else { return }
                    
                    allObjects.forEach({ (snapshot) in
                        let uid = snapshot.key
                        
                        Database.fetchUser(with: uid, completion: { (user) in
                            self.users.append(user)
                            self.tableView.reloadData()
                        })
                    })
                    self.userCurrentKey = first.key
                }
            }
        } else {
            USER_REF.queryOrderedByKey().queryEnding(atValue: userCurrentKey).queryLimited(toLast: 5).observeSingleEvent(of: .value, with: { (snapshot) in
                
                guard let first = snapshot.children.allObjects.first as? DataSnapshot else { return }
                guard var allObjects = snapshot.children.allObjects as? [DataSnapshot] else { return }
                allObjects.removeAll(where: { $0.key == self.userCurrentKey })
                
                allObjects.forEach({ (snapshot) in
                    let uid = snapshot.key

                    if uid != self.userCurrentKey {
                        Database.fetchUser(with: uid, completion: { (user) in
                            self.users.append(user)
                            if self.users.count == allObjects.count  {
                                self.tableView.reloadData()
                            }
                        })
                    }
                })
                self.userCurrentKey = first.key
            })
        }
    }

推荐答案

我找到了一种方法。在Firebase规则中，我是这样解决这个问题的：

  "$users": {
    "$uid": {
".read": "auth != null && !(root.child('blocked-users').child(auth.uid).hasChild($uid))",
".write": "auth != null"
}
}

内容如下：如果auth不为空，并且用户不在其要查找的用户的阻止用户集合中，则允许该用户读取该用户的数据。

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