孩子的Swift Firebase查询孩子[重复]

Question

所以我在这里被困了半天，我试图获得 Arya 的所有主题，但我很难做到。

这是 Firebase 中的示例结构。

-Subjects
    -math
        id: 1
        name: Math
        -students
            -Arya
                id: 1
                name: Arya
            -JonSnow
                id: 2
                name: JonSnow
            +justsomename
    +science
    +english
    +history
    +computer

然后我找到了这个Querying in Firebase by child of child。

我试过了

ref.queryOrdered(byChild: "students/name").queryEqual(toValue: "Arya").observeSingleEvent(of: .value, with: { snapshot in

        print(snapshot)
    })

ref == 主题

但这就是回报

Snap (subjects) <null>

查询是否正确，我只是做错了什么？

Answer 1

也许像这样的东西......可以工作......

var subjects = [String]()

    ref.observeSingleEvent(of: .value, with: { snapshot in

        let value = snapshot.value as? NSDictionary
        let postsIds = value?.allKeys as! [String] // this will put all the subjects such as math into an array called postIDs

        for postId in postsIds { //this is going to cycle through the array and check each one for your student
            let refToPost = Database.database().reference(withPath: "Subjects" + postId)
            refToPost.observeSingleEvent(of: .value, with: { snapshot in
                if snapshot.hasChild("Arya") {



                    self.subjects.append(snapshot)
                }
            })
        }
    })
  print("this is the ist of subjects with my student: \(subjects)")