Firebase 的云功能：如何获取 event.data.ref.parent.child("xxx").val？

Question

我在 Firebase 上有这样的结构：

members
 |- -kSjJSDFjl2DFc
          |- isDeleted: true
          |- gender: "male"

在我的云函数中，我写道：

exports.doMemberDeletion = functions.database.ref("/members/{memberId}/isDeleted").onWrite(event => {
    const isDeleted = event.data.val();

    if (isDeleted) {
        const gender = event.data.ref.parent.child("gender").val; // Error here
        console.log("Deleted a " + gender + " member");
    }
});

但是，它在event.data.ref.parent.child().val 上给出错误，请告知在这种情况下如何获取该值。谢谢！

Answer 1

用户是否有权访问父级？如果不是，请使用 event.data.adminRef 代替 event.data.ref 以不受限制地访问数据库。请参阅the documentation 了解更多信息。

Answer 2

事件数据中提供的DeltaSnapshot 仅适用于匹配的位置。树或同级中较高的数据不可用。如果您的成员数据不是太大以至于您担心监听其中的任何更改，您可以这样做：

// listen one level higher in tree    
exports.doMemberDeletion = functions.database.ref("/members/{memberId}").onWrite(event => {
    const wasDeleted = event.data.previous.child('isDeleted').val();
    const isDeleted = event.data.current.child('isDeleted').val();

    if (!wasDeleted && isDeleted) {
        const gender = event.data.current.child('gender').val();
        console.log("Deleted a " + gender + " member");
    }
});

您的原始方法也有效，但需要获取性别数据：

exports.doMemberDeletion = functions.database.ref("/members/{memberId}/isDeleted").onWrite(event => {
    const isDeleted = event.data.val();

    if (isDeleted) {
        // as noted in Jen Person's answer, use adminRef for unrestricted access
        return event.data.adminRef.parent.child('gender').once('value').then((snapshot) => {
           console.log("Deleted a " + snapshot.val() + " member");
        });
    }
});