Firebase - 如何遍历 snapshot.hasChild("...")

Question

我的数据库如下所示

users
  |
  @--uidABC
       |
       |---phone:"+13125550690"
       |
       |---followers
              |
              |----uid123
              |      |---timeStamp:111222
              |
              |----uid456
              |      |---timeStamp:777999

我使用.observeSingleEvent 检查uidABC 是否存在，如果存在，我想检查该路径下是否有一个名为followers 的child。

我可以使用snapshot.hasChild("followers") 来查看它是否可用以及是否可用如何循环遍历下面的所有子节点 snapshot.hasChild("...")？

我使用下面的代码，但它循环了错误的snapshot。当它应该使用DataSnapshot 在followers 下的任何内容时，它会使用顶级一级

let ref = Database...child("users").child(uidABC)
ref.observeSingleEvent(of: .value, with: { (snapshot) in

    if !snapshot.exists() {

        // this user doesn't exist
        return
    }

    if !snapshot.hasChild("followers") {

       // this user exists but has no followers
       return
    }

    // this user exists and has followers now loop through them
    for uid in snapshot.children {

        let snapshot = uid as! DataSnapshot

        if let dict = snapshot.value as? [String:Any] {
            let timeStamp = dict["timeStamp"] as? Double
            // eg. check for a specific timeStamp
         }
     }
})

Answer 1

我从here 和这里得到了答案

let ref = Database...child("users").child(uidABC)
ref.observeSingleEvent(of: .value, with: { (snapshot) in

    if !snapshot.exists() {

        // this user doesn't exist
        return
    }

    if !snapshot.hasChild("followers") {

        // this user exists but has no followers
        return
    }

    // this user exists and has followers now loop through them
    let childSnapshot = snapshot.childSnapshot(forPath: "followers") {

    for child in childSnapshot.children {

        let snap = child as! DataSnapshot

        let uid = snap.key

        if let dict = snap.value as? [String: Any] {

            let timeStamp = dict["timeStamp"] as? Double ?? 0
            // eg. check for a specific timeStamp
        }
    }
})

Answer 2

使用child：

// this user exists and has followers now loop through them
for uid in snapshot.childSnapshot("followers") {

    guard let snapshot = uid as! DataSnapshot else {
     // Followers error
    }

    if let dict = snapshot.value as? [String:Any] {
        let timeStamp = dict["timeStamp"] as? Double
        // eg. check for a specific timeStamp
     }
 }

您可以在此处找到更多信息： Iterate over snapshot children in Firebase