CODEWITHSUNDEEP
fluttergoogle-cloud-firestore
Gireesh
Gireesh

Reputation: 181

Flutter - _CastError (type 'List<dynamic>' is not a subtype of type 'List<Map<String, dynamic>>' in type cast)

I stored a list of Map data in firestore database. But when I tried to fetch the data to a variable of type List<Map<String, dynamic>>, it shows the error "_CastError (type 'List' is not a subtype of type 'List<Map<String, dynamic>>' in type cast)".

Here is the code,

// code to fetch objects list from database
Future<List<Map<String, dynamic>>> getUserObjects() async {
    Map<String, dynamic> userInfo = await getUserInfo();
    List<Map<String, dynamic>> userObjects = userInfo['objects'] as List<Map<String, dynamic>>;
    List<Map<String, dynamic>> result = [];
    for(var i=0; i<userObjects.length; i++) {
      var docInfo = await DatabaseMethods().getDocumentInfo(findCollectionName(userObjects[i]['objectType']), userObjects[i]['docId']) as Map<String, dynamic>;
      result.add({'icon': findIcon(userObjects[i]['objectType']), 'objectName' : docInfo['objectName'], 'docId' : userObjects[i]['docId']});
    }
    return result;
  }


Future<Map<String, dynamic>> getUserInfo() async {
    var user = await FirebaseAuthentication().getCurrentUser();
    Map<String, dynamic> userInfo = await DatabaseMethods().getuserFromDB(user.uid);
    if(userInfo['objects'] == null) {
      userInfo.addAll({'objects' : []});
    }
    return userInfo;
  }

final FirebaseAuth auth = FirebaseAuth.instance;

  Future<User> getCurrentUser() async {
    return auth.currentUser!;
  }

// code to add an object to object list in collection 'user'

Future<void> updateUserObjectList(Map<String, dynamic> object) async {
    var user = await FirebaseAuthentication().getCurrentUser();
    var userId = user.uid;
    await FirebaseFirestore.instance.collection('users').doc(userId)
      .update({'objects' : FieldValue.arrayUnion([object])});
  }

The data stored in the database will look like the below image with the following changes,

  1. replace 'quotes' with 'objects'
  2. replace 'auther' with 'objectType'
  3. replace 'quote' with 'docId'
  4. replace 'user' with 'users'

enter image description here

Can someone say where the error happened. Code gives the error in the line "List<Map<String, dynamic>> userObjects = userInfo['objects'] as List<Map<String, dynamic>>;" in getUserObjects method

Upvotes: 0

Views: 202

Answers (1)

ErnestoC
ErnestoC

Reputation: 2904

Moving the OP's solution into an answer for this question, this specific issue was caused by sending an incorrect document.id in the fetch call.

Using the correct document ID (user.id + datetime for the OP's case) solved the problem.

Upvotes: 1

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