如何仅删除Firebase值的父键？

Question

我对使用Firebase相当陌生，我正在努力只访问父键以删除该值。

我目前正在尝试使用以下代码访问父密钥：

if let exerciseName = exercises[indexPath.row].exerciseName {

    let ref = FIRDatabase.database().reference().child("userExercises")

    ref.queryOrdered(byChild: "exerciseName").queryEqual(toValue: exerciseName).observe(.childAdded, with: { (snapshot) in

            print(snapshot.ref)

    })

}

我的数据结构如下：

。

但是当我打印出值时，如果数据库中有另一个用户具有相同的exerciseName，则会打印出所有父键。

如何删除我选择删除的记录？

当我print(snapshot)时，结果为：

Snap (-KWw9hg2Uiyo9_cj7TAy) {
    bodyPart = Back;
    exerciseName = "Test 2";
    userId = 8rHmyTxdocTEvk1ERiiavjMUYyD3;
}
Snap (-KWwAGd3t9vsW0LHKtV1) {
    bodyPart = Arms;
    exerciseName = "Test 2";
    userId = PO8p0UoqqHOas3D9Ise8CgWT3PN2;
}

Answer 1

尝试：

    let ref = FIRDatabase.database().reference().child("userExercises")        
    let filteredRef = // do some query,sorting ...

    filteredRef.observe(.value, with: { snapshot in
        for item in snapshot.children {
            guard let itemSnapshot = item as? FIRDataSnapshot else { break }
            guard let dict = itemSnapshot.value as? NSDictionary else { break }

            let id = itemSnapshot.key // this is the record id of an exercise !
        }
    }

删除您的一条记录：

    let ref = FIRDatabase.database().reference().child("userExcercises").child(record_id) // see above how to fetch the id
    ref.removeValue()

我建议你重新构建你的userExcercises：

{
    "userExcercises" : {
        "<USER-ID>" : {
            "<EXCERCISE-ID>" : {
                "bodyPart" : "Back",
                "excerciseName" : "Test02"
            },
            // lots of more excercises for this user ...
        },
        // lots of more users ...
     }
}

要明确：USER-ID是经过身份验证的用户的uid，EXCERCISE-ID是自动生成的（childByAutoId（））id