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检查是否存在uidABC，如果存在，我想检查该路径下是否存在名为child的{{1}}。

我可以使用followers来查看它是否可用以及是否如何遍历下面的所有子对象 snapshot.hasChild("followers")？

我使用下面的代码，但是它遍历了错误的snapshot.hasChild("...")。当它应使用snapshot下的任何DataSnapshot

时，它会使用最高一级

followers

Answer 1

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

Answer 2

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
        }
    }
})

Firebase-如何遍历snapshot.hasChild（“ ...”）

2 个答案: