如何在我的 Flutter 应用程序中使用我的数据模型？

Question

I am new to this so I do apologize. But I created a Firebase Firestore data model to represent my article post from Firestore. When I type it into the AppBar's title section, I am getting an error. How do you work with this? I would appreciate any sort of help or hints as I am new to this so I am still learning. I have also downloaded all the required dependencies for this.

My Firestore database screen in case if this is also needed

This is my Post model which models my articles from my Firestore database.

class Post {

String title;
  String imageURL;
  String text;



Post({this.title, this.imageURL, this.text});

  factory Post.fromFirestore(DocumentSnapshot doc) {
    var data = doc.data();

return Post(
  title: data['title'],
  imageURL: data['imageURL'],
  text: data['text']
);
  }

}

This is my article page (ReaderPage)

// This page displays article to the user.
class ReaderPage extends StatelessWidget {

  CollectionReference posts = FirebaseFirestore.instance.collection('posts');



@override
  Widget build(BuildContext context) {
return Scaffold(
  appBar: AppBar(
    // This line is causing errors...
    title: Post.fromFirestore().title,
  ),
  body: Container(

  ),
);
  }
}

Answer 1

The model is correct, but you are not reading from Firestore. You could use a FutureBuilder to build the content only when the promise given by the firestore query has been resolved:

return FutureBuilder<DocumentSnapshot>(
  future: posts.doc(documentId).get(),
  builder:
      (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {

    if (snapshot.hasError) {
      return Text("Something went wrong");
    }

    if (snapshot.connectionState == ConnectionState.done) {
      Map<String, dynamic> data = snapshot.data.data();
      return return Scaffold(
        appBar: AppBar(
        title: data.title,
      ),
      body: Container(

      ),
    );
    }

    return Text("loading");
  },
);

But in this way you are not using the model you have created.

In my opinion the best way could be implement a DatabaseService class:

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'dart:async';
import 'posts.dart';

class DatabaseService {
  final Firestore _db = Firestore.instance;

  /// Get a stream of a single document
  Stream<Post> streamPost(String uid) {
    return _db
        .collection('posts')
        .document(uid)
        .snapshots()
        .map((snap) => Post.fromFirestore(snap.data));
  }

  /// Query a subcollection
  Stream<List<Post>> streamPost(String uid) {
    var ref = _db.collection('posts');

    return ref.snapshots().map((list) =>
        list.documents.map((doc) => Post.fromFirestore(doc)).toList());
    
  }

} 

But in this way you have to work with streams. I suggest you to have a look at this library: Flutter Provider And this article could help you: Here