CODEWITHSUNDEEP
firebaseflutterdartgoogle-cloud-firestorestream-builder
AAM
AAM

Reputation: 19

Firestore Nested Query in Flutter for List Building

I have two collections in my firestore db; "queries" and "users". My requirement is to get all the queries with respect to specific flag from "queries" collection. Once done I need to check uid in each query and query my user's data using that uid from "users" collection. In this case I am fetching user's name and number using StreamBuilder in flutter. Below is my approach: 

return new StreamBuilder(
  stream: db.collection("queries").where("isAttended", isEqualTo: false).snapshots(),
  builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot){
    if(!snapshot.hasData) return new Text("Loading...");
    return new ListView(
      children: snapshot.data.documents.map((document){
        String name = '';
        String number = '';
        var doc = db.collection("users").document(document["uid"]).get();
        doc.then((onValue) {
          number  = onValue.data['number'];
          name = onValue.data['name'];
        });
       return new ListTile(
         title: new Text(name),
         subtitle: new Text(number),
       ); 
      }).toList(),
    );
  },

);

Problem is onValue returns null. Please advise on my approach for querying data in the manner I specified above. TIA.

Upvotes: 1

Views: 2430

Answers (1)

ibrahimkarahan
ibrahimkarahan

Reputation: 3015

Lets start,

This is your children list List<Widget> children = [];

Change your ListView children to ListView(children: children, ...)

And update your streambuilder like that,

if(!snapshot.hasData) return new Text("Loading...");
initChildren(snapshot); // here is important
return new ListView(...

And initChildren is

initChildren(snapshot) async {
  final list = await Future.wait(snapshot.data.documents.map((document) async {
    String name = '';
    String number = '';
    var doc = await db.collection("users").document(document["uid"]).get();
    doc.then((onValue) {
      number = onValue.data['number'];
      name = onValue.data['name'];
    });
    return new ListTile(
      title: new Text(name),
      subtitle: new Text(number),
    );
  }));
  setState(() => children = list);
}

Upvotes: 1

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