ios - 想要从 firebase 数据库中提取 QR 值，但快照打印 nil

Question

我想提取 Firebase 数据库中的 QR 值 QR Values->year->month->day->QR : value

func GetQR() {
    let date = getDate()

    let year =  String(describing: date.year)
    let month = String(describing:date.month)
    let day = String(describing:date.day)

    ref = Database.database().reference().child("QR Values").child(year).child(month).child(day)
    ref.observeSingleEvent(of: .value, with: { (snapshot) in

        // Get user value
        let value = snapshot.value as? String


            print(value)

    })
    { (error) in
        print(error.localizedDescription)
    }

    }

打印的快照为零。

Answer 1

您仍然需要在 snapshot 中查找 QR 属性。您从数据库中获取的信息:

ref = Database.database().reference().child("QR Values").child(year).child(month).child(day)
ref.observeSingleEvent(of: .value, with: { (snapshot) in
    let value = snapshot.childSnapshot(forPath: "QR").value as? String