type "List<dynamic>" is not a subtype of type "List<Widget>"

Understanding the Error: type 'List<dynamic>' is not a subtype of type 'List<Widget>'

So, you've got some code that you copied and pasted from a Firestore example and you're encountering an error that says: type 'List<dynamic>' is not a subtype of type 'List<Widget>'. 🤔

This error typically occurs when there's a mismatch between the expected type and the actual type being used. In this case, it seems that you're trying to assign a list of dynamic objects (List<dynamic>) to a property or variable expecting a list of Widget objects (List<Widget>).

Let's break it down and find a solution! 💪

Understanding the Code

First, let's take a closer look at the code snippet you provided:

Widget _buildBody(BuildContext context) {
  return new StreamBuilder(
    stream: _getEventStream(),
    builder: (context, snapshot) {
      if (!snapshot.hasData) return new Text('Loading...');
      return new ListView(
        children: snapshot.data.documents.map((document) {
          return new ListTile(
            title: new Text(document['name']),
            subtitle: new Text("Class"),
          );
        }).toList(),
      );
    },
  );
}

In this code, you're using a StreamBuilder to build a widget that listens to a stream (_getEventStream()) and rebuilds itself whenever new data arrives. Inside the builder, you're checking whether the snapshot has data and returning either a loading indicator (Text('Loading...')) or a ListView containing a list of ListTile widgets.

Identifying the Problem

The error you're encountering indicates that the children property of the ListView is expecting a List<Widget>, but you're providing a List<dynamic>. This suggests that the documents.map() function is returning a list of dynamic objects instead of widgets.

Finding the Solution

To resolve this issue, you need to ensure that the map() function returns a list of widgets. In this case, you can explicitly convert each document into a ListTile widget using the toList() function.

Here's the modified code:

Widget _buildBody(BuildContext context) {
  return StreamBuilder(
    stream: _getEventStream(),
    builder: (context, snapshot) {
      if (!snapshot.hasData) return Text('Loading...');
      return ListView(
        children: snapshot.data.documents.map<Widget>((document) {
          return ListTile(
            title: Text(document['name']),
            subtitle: Text("Class"),
          );
        }).toList(),
      );
    },
  );
}

By specifying <Widget> as the generic type argument for the map() function (map<Widget>((document) {...) and using the toList() function, you ensure that the children property of the ListView receives a List<Widget>, thus resolving the error.

The Call-to-Action: Let's Engage!

I hope this solution helped you resolve the type 'List<dynamic>' is not a subtype of type 'List<Widget>' error. 💡

If you found this blog post helpful, don't forget to share it with your fellow developers who might encounter a similar issue. 😄❤️

Feel free to leave a comment below if you have any questions or if there's anything else I can assist you with. Happy coding! 🚀👨‍💻