FLUTTER FIRESTORE -Query the field and get document id and check other field - flutter

Question

am trying to get the searched value(userid) which is in the field of a document in firestore I want to check the other fields(status) of the document I tried this method but failed
handlesubmit(BuildContext context)async{
final QuerySnapshot searcheduserid=
await Firestore.instance.collection('users')
.where('userid',isEqualTo: userid).limit(1).getDocuments();
final userdocid=searcheduserid.documents.map((doc)=>doc.documentID);
final DocumentSnapshot getuserdoc= await Firestore.instance.collection('users')
.document(userdocid).get();
final userstatus = getuserdoc.data['status'];
// I GET AN ERROR HERE ERROR SAYS
// METHOD [](status) was called on null
if(userstatus==null){
return showdialog( context,'the entered user id status does not exist');
}
}

Answer 1

You probably copied an older version of your code because it is unlikely that your code compiles the following line of your program:
final DocumentSnapshot getuserdoc= await Firestore
.instance
.collection('users')
.document(userdocid).get();
The error message on my system is:
The argument type 'Iterable<String>' can't be assigned to the parameter type 'String'.
Which means that userdocid is an Iterable of type String (Iterable<String>), but a parameter which is of type String is expected.
You have multiple options of fixing the problem, but I suggest the following:
Since you are only expecting one document from your QuerySnapshot it is enough to just look at the first document.
final QuerySnapshot searchedUserId = await Firestore.instance
.collection('users')
.where('userid', isEqualTo: userid)
.limit(1)
.getDocuments();
// if it is possible that searchedUserId returns no document make sure to
// check whether searchedUserId.documents.length > 0,
// otherwise searchedUserId.documents.first will throw an error
DocumentSnapshot document = searchedUserId.documents.first;
final userDocId = document.documentID;
final DocumentSnapshot getuserdoc =
await Firestore.instance.collection('users').document(userDocId).get();
Improved Solution:
However I think your code is a bit redundant anyways, because you are looking up a field of a document which has the same value as the document ID. You could shorten the whole code to
final DocumentSnapshot getuserdoc =
await Firestore.instance.collection('users').document(userid).get();
Error calling getuserdoc.data['status']
If you get an error saying something similar to
[](status) was called on null
Then that means getuserdoc has no value. This is likely due to the fact that there is no such database entry with the given ID. Check if the ID is in your database, otherwise comment below for additional information, because the provided code had compilation errors and does not run at all.