如何从 firebase 中的引用文档中检索数据？

Question

I'm relatively new to firebase, and I'm trying to retrieve data from a referenced document in another collection to show up. https://drive.google.com/file/d/1CcGCPgO9JVd6iCA_1FHfO95J2_E19Z0I/view?usp=sharing https://drive.google.com/file/d/1tM5g_A8jcfKTMWMczaS_35gjNcDn_Ho1/view?usp=sharing

this is how i add a student and the parent's ID

const newStudent = {
    name: req.body.name,
    grade: req.body.grade,
    //status: `no parent request`,
    parentId:db.doc(req.body.parentId),
    gender:req.body.gender,
    //parentName:req.body.parentName,
    transporation:req.body.transporation,
    userHandle: req.user.handle
  };

what I'm trying to do is retrieve the name of the parent I'm referencing in the student document, I tried the following but it gave me the entire snapshot of the parent, i tried a lot of methods but none of them work

(req, res) => { db.collection("students")
   [.orderBy("grade", "desc")
    .get()
    .then((data) => {
     let students = \[\];
     //const {parentname} = db.collection('parent').doc.data().name;
      data.forEach((doc) => {
      var parentId = doc.data().parentId.id;][1]
  
  db.collection("parent").get().then((pdata) => {
    pdata.forEach((pdoc) => {
      students.push({
        parentname: parentId});});});
  students.push({
    studentId: doc.id,
    name: doc.data().name,
    grade: doc.data().grade,
    //parentName:parentname
    // parentName:doc.data().parentId.id,
    
  });
});
return res.json(students); })

any advice or help is much appreciated.

Answer 1

Here what you are doing is, you are calling the whole data inside the document you are calling.
So you have to explicitly call the particular object of the document.

//TODO: change the docName to desired document id
db.collection("parent").doc('docName').collection('name').get().then((pdata) => {
    pdata.forEach((pdoc) => {
      students.push({
        parentname: parentId});});});
  students.push({
    studentId: doc.id,
    name: doc.data().name,
    grade: doc.data().grade,
    //parentName:parentname
    // parentName:doc.data().parentId.id,
    
  });

Here I am referring to the particular document of which the data is to be retrieved.