Hello guys I am using a stream builder to get data from fireStore collection to display some posts but I am getting an error saying type 'Null' is not a subtype of type 'String' and the value of the snapshot is null

this is the post model that I have

class Post {


 final String id;
  final String description;
  final String validUntil;
  final String availableFor;
  final String imageUrl;
  final String owner;



Post({
    required this.id,
    required this.description,
    required this.validUntil,
    required this.availableFor,
    required this.imageUrl,
    required this.owner,
  });

  Map<String, dynamic> toJson() => {
        'id': id,
        'description': description,
        'validUntil': validUntil,
        'availableFor': availableFor,
        'imageUrl': imageUrl,
        'owner': owner,
      };

  static Post fromJson(Map<String, dynamic> json) => Post(
        id: json['id'],
        description: json['description'],
        validUntil: json['validUntil'],
        availableFor: json['availableFor'],
        imageUrl: json['imageUrl'],
        owner: json['owner'],
      );
}

and this is the Stream

Stream<List<Post>> readPosts() => FirebaseFirestore.instance
  .collection('posts')
  .snapshots()
  .map((snapshot) =>
      snapshot.docs.map((doc) => Post.fromJson(doc.data())).toList());

and this is the StreamBuilder

StreamBuilder<List<Post>>(
                stream: readPosts(),
                builder: (context, snapshot) {
                  if (snapshot.connectionState == ConnectionState.active) {
                    if (snapshot.data == null) {
                      print(snapshot.error.toString());
                      return Text(snapshot.error.toString());
                    } else {
                      final posts = snapshot.data;
                      return Column(
                        children: posts!.map(buildPost).toList(),
                      );
                    }
                  } else {
                    return Center(
                      child: CircularProgressIndicator(),
                    );
                  }
                })

I would really appreciate it if you can help me solve this problem

CodePudding user response：

Likely one of the values in the Post is null in Firebase, such as description or imageUrl. Print the doc to try troubleshooting the problem like this:

Stream<List<Post>> readPosts() =>
    FirebaseFirestore.instance.collection('posts').snapshots().map((snapshot) {
      print(snapshot);
      return snapshot.docs.map((doc) {
        print(doc.data());
        return Post.fromJson(doc.data());
      }).toList();
    });

CodePudding user response：

As i seen in your code you have created model which not-null type model create nullable model for that you can use