Future builder flutter firebase error: A value of type 'Iterable<BlogPost>' can't be assigned to a variable of type 'List<BlogPost>'

Issue

I am having an issue with creating a future builder. I am trying to create a List of Documents to show in a ListView but I can not find away to create the List in the custom class I have created(BlogPosts).

I keep receiving this error:

Error: A value of type 'Iterable<BlogPost>' can't be assigned to a variable of type 'List<BlogPost>'.

here is my code:

CollectionReference postsRef = FirebaseFirestore.instance.collection('posts');
late List<BlogPost> posts;

FutureBuilder(
          future: postsRef.get().then((val) {
              posts = val.docs.map((doc) => BlogPost.fromDocument(doc));
            }),
          builder: (context, snap) {
            if(snap.connectionState == ConnectionState.done) {
              return ListView.builder(
                physics: BouncingScrollPhysics(),
                  itemCount: 3,
                  itemBuilder: (context, index) {
                  return Text('data);
                  }
              );
            } else {
              return Center(
                child: Text('Loading')
              );
            }
          }
        )

here is the code for my custom class:

class BlogPost {
  String displayName;
  String postmsg;
  String postId;
  String UserId;

  BlogPost(this.displayName, this.postmsg, this.postId, this.UserId);

  factory BlogPost.fromDocument(DocumentSnapshot doc) {
    return BlogPost(
        doc['displayName'],
        doc['postmsg'],
        doc['postId'],
        doc['UserId']
    );
  }
}

Solution

The map() function returns an Iterable. To turn that into a list, call toList() on its result. So:

posts = val.docs.map((doc) => BlogPost.fromDocument(doc)).toList()

Answered By – Frank van Puffelen

Answer Checked By – Candace Johnson (FlutterFixes Volunteer)