無法從 firestore flutter 檢索數據

Question

String branch, semester;



Future<void> _getUserDetails() async {
String uid = FirebaseAuth.instance.currentUser.uid;
await FirebaseFirestore.instance.collection('UserDatabase').doc(uid).get().then((user) {
  setState(() {
    branch = user.data()['Branch'];
    semester = user.data()['Semester'];
  });
});

print(branch);
print(semester);

}

這是我的數據庫firestore 快照的快照

我正在嘗試從 firestore 檢索數據，但出現此錯誤

未處理的異常：NoSuchMethodError：在 null 上調用了方法“[]”。

有人可以幫我解決這個錯誤。

Answer 1

確保 uid 在 firestore 中作為文檔可用

或者你可以試試下面的代碼

  Future<void> _getUserDetails() async {
    String uid = FirebaseAuth.instance.currentUser.uid;
    DocumentSnapshot doc = await FirebaseFirestore.instance.collection('UserDatabase').doc(uid).get();

    if(doc.exists) { // this will check availability of document
      branch = doc.data()['Branch'];
      semester = doc.data()['Semester'];
    }else{
      branch = "User is not available";
      semester = "User is not available";
    }
    setState((){});
  }

---

登記：

_firestore.collection('UserDatabase').doc(FirebaseAuth.instance.currentUser.uid).set({
 'Branch': branchVal,
'Email': loggedInUser.email,
'RollNo': rollNoVal,
'Semester': semesterVal,
'Year': yearVal,
});

Answer 2

試試這個

await FirebaseFirestore.instance.collection('UserDatabase').doc(uid).get().then((user) {
user.docs.forEach((result) {
  branch = result.data()['Branch'];
semester = result.data()['Semester'];
});

});