Following error occured for Firebase Cloudstore . I cant map a list function to Stream list todo The argument type 'List? Function(QuerySnapshot<Object?>)' can't be assigned to the parameter type 'List Function(QuerySnapshot<Object?>)'.

import 'dart:math';

import 'package:cloud_firestore/cloud_firestore.dart';

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:todolist/models/model.dart';

class databaseService {
  CollectionReference todosCollection =
      FirebaseFirestore.instance.collection("Todos");

  Future createNewTools(String title) async {
    await todosCollection.add({
      "title": title,
      "iscomplete": false,
    });
  }

  Future completTask(id) async {
    await todosCollection.doc(id).update({"iscomplete": true});
  }

  Future removeTodo(uid) async {
    await todosCollection.doc(uid).delete();
  }

  List<Todolist>? todoFromFirestore(QuerySnapshot snapshot) {
    if (snapshot != null) {
      return snapshot.docs.map((e) {
        return Todolist(
                iscomplete: e["iscomplete"],
                title: e["title"],
                id: e.id,
        );
      }).toList();
    } else {
      return null;
    }
  }

  Stream<List<Todolist>> listTodo(){
    return todosCollection.snapshots().map(todoFromFirestore); //error
  }

  }

and the todolist model file:

class Todolist {
  String id;
  String title;
  String iscomplete;

  Todolist({required this.id, required this.title, required this.iscomplete, isComplete});
}

error:

CodePudding user response：

  List<Todolist> todoFromFirestore(QuerySnapshot snapshot) {
    if (snapshot != null) {
      return snapshot.docs.map((e) {
        return Todolist(
                iscomplete: e["iscomplete"],
                title: e["title"],
                id: e.id,
        );
      }).toList();
    } else {
      return [];
    }
  }

A nullable List is causing the error. Try This...