子数组中的查询对象

Question

I am trying to use a query to retrieve data of student who are only 4 years old from my database but i cant figure out how to use Firebase to query the age (The array in each child).

{
  "student" : {
    "-Kv2RVDDsI-v6V7g_LBn" : [ {
      "name" : "sam",
      "age" : "6"
    }, {
      "name" : "tom",
      "age" : "4"
    }
   ],
   "-hguyu-v6V7g_LBn" : [ {
      "name" : "Tim",
      "age" : "12"
    }, {
      "name" : "tom",
      "age" : "4"
    }
   ]
  }
}

This is my code but it does no return anything.

ref.child("student").queryOrdered(byChild: "age").queryEqual(toValue: 4).observe(.childAdded,  with: { (snapshot) in
        let value = snapshot.value
        print(value)
    }) { (error) in
        print(error.localizedDescription)
}

However, if i remove the queryOrdered(byChild: "age") it works.

Thanks.

Answer 1

You are referencing "Student" when actually your JSON database format child path name is "Students".

Also make sure that you are querying by key. Refer to the Firebase documentation to see how to query by key. I don't understand your structure though why you have 2 children per key.

Why not have a new key for each child?