swift - 在 swift/firebase 项目中，当使用 .observe 而不是使用 SingleEvent 时，是什么导致数组可读？

Question

因此，当在下面的第一个快照（见粗体）中使用 Single Event 时，第一个快照无法拾取 array1（来自第二个快照）。但是当使用 .observe 时，它​​可以。为什么会这样？

起初我不明白为什么 Single Even 会失败，但 .observe 不会。我做了很多打印，发现第二张快照效果很好。但如果使用 .SingleEvent，则无法识别第二个快照中的 array1。但是，如果改为使用 .observe，则可以识别。

/////第一个快照

let thisUsersUid = Auth.auth().currentUser?.uid //Mr. Dunn's uid

refArtists = Database.database().reference().child("people");

**refArtists.observeSingleEvent**(of: .value,  with: { [weak self]snapshot in


if snapshot.childrenCount>0{

self.people.removeAll()

for people in snapshot.children.allObjects as! [DataSnapshot] {
    
    if people.key != thisUsersUid {
        print("peoplekey",people.key)
        
        let peopleObject = people.value as? [String: AnyObject]
        let peopleEducation = peopleObject?["Education"] as? String
        ...
        let userId = people.key
        
        ...
        
        if Calendar.current.isDateInToday(date) {
            let distance = locCoord.distance(from: self.dict)
            print(distance, "distancexy")
            
            if distance/1609.344 < 3000 && self.array1.contains(people.key){
                print(self.array1, "f111111")
                
                print("fee", self.dict )
                print(distance, "distancexy")
                
                let peopl = Userx(Education: peopleEducation, .......)
                
                self.people.append(peopl)
                let d = people.key
                self.printPersonInfo(uid:d)
                
            } else {
                print ("w")
            }
        } else {
            print ("alpha")
        }
    }

    print("aaaaaaaa", self.people.map {$0.distance})
}
self.people.sort { ($0.distance ?? 0) < ($1.distance ?? 0) }
}
})

//////第二个快照使array1成为第一个快照

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

        refArtists = Database.database().reference().child("people").child(myUid).child("e2")
        
        refArtists.observeSingleEvent(of:.value,  with: {snapshot in
            
           let myDomain = snapshot.value as? String
            self.bSnap = myDomain
            print("haaal", self.bSnap)

            
            
                           let peopleRef = Database.database().reference().child("people")
                           let thisPersonRef = peopleRef.child(myUid).child("e2")
                           thisPersonRef.observeSingleEvent(of:.value,  with: {snapshot in
                               
                                   if snapshot.exists() {

        

            let query = Database.database().reference().child("people").queryOrdered(byChild: "e2").queryEqual(toValue: self.bSnap)
          query.observeSingleEvent(of: .value, with: { snapshot in
              var allUsers = snapshot.children.allObjects as! [DataSnapshot]
              ///////end (1) of comment
              if let index = allUsers.firstIndex(where: { $0.key == myUid } ) {
                  allUsers.remove(at: index) //remove the current user
              } /////end (2) of comment
                
                for userSnap in allUsers {
                    let name = userSnap.childSnapshot(forPath: "postID").value as? String
                    print(name, "NNN")

                if let unwrappedName = name {
                    **self.array1.append(unwrappedName)**
                }
                }

            print(self.array1, "ahah")
                
              
            
            
            })
                                    
                                   } else {
                            print("no")
                                    
                            }
          })

      })

标签： swiftfirebasefirebase-realtime-databasefirebase-authenticationsnapshot