I am trying to build an app using Flutter and Firestore. When loading a Collection from Firestore using StreamBuilder to display it in a ListView, I get the following error
The following assertion was thrown building StreamBuilder<QuerySnapshot>(dirty, state:
I/flutter (26287): _StreamBuilderBaseState<QuerySnapshot, AsyncSnapshot<QuerySnapshot>>#d5638):
I/flutter (26287): type '_InternalLinkedHashMap<dynamic, dynamic>' is not a subtype of type 'Map<String, dynamic>'
I/flutter (26287): where
I/flutter (26287): _InternalLinkedHashMap is from dart:collection
I/flutter (26287): Map is from dart:core
I/flutter (26287): String is from dart:core
This is how I want to get data from the DocumentSnapshot
class Creator {
const Creator({this.creatorId, this.name});
Creator.fromDoc(DocumentSnapshot doc) : this.fromMap(doc.data);
Creator.fromMap(Map<String, dynamic> map) :
assert(map.containsKey('creatorId'),
assert(map.containsKey('name'),
this ( creatorId: map['creatorId'], name: map['name'] );
/*
...
*/
}
And how I want to use it
return Scaffold(
appBar: AppBar(title: new Text('Creators')),
body: StreamBuilder<QuerySnapshot>(
stream: CreatorRepo.getCreators().map<List<Creator>>((creators) {
return creators.documents.map<Creator>((c) => Creator.fromSnapshot(c)).toList();
}),
builder: (BuildContext context, snapshot) {
if ( snapshot.hasData ) {
return ListView.builder(
itemCount: snapshot.data.length,
builder: (context, index) {
final creator = snapshot.data[index];
return ExpansionTile(
title: Text(creator.name),
children: [
Text(creator.creatorId),
],
);
},
);
}
return const CircularProgressIndicator();
},
),
);
Dependencies:
dependencies:
flutter:
sdk: flutter
cloud_firestore: ^0.6.3
firebase_messaging: ^0.2.4
Firestore only allows for String
keys and dynamic
values being, with the exception of Timestamp
, core language types. The cloud_firestore
plugin keeps document data in an _InternalLinkedHashMap<dynamic, dynamic>
. I thought that the Map
inside all DocumentSnapshot
would be Map<String, dynamic>
. How can I work around this? Changing all functions to take Map<dynamic, dynamic>
and assume the key is a String
is a rather ugly workaround to the problem.
I believe this is because the Map returned from Firebase is not a Map<String, dynamic>
but instead Map<dynamic, dynamic>
.
See https://github.com/flutter/flutter/issues/17417 for a related issue.
Use Map<String, dynamic>.from ( mapFromFirestore )
. This creates a new Map<String, dynamic>
from the contents of mapFromFirestore
, throwing an error if it finds a key that isn't a String
.
I too had this problem and fixed it with --
Map<String, dynamic> var = {'item': 0, 'name': 'John'}
instead of Map unspecified.
Map var = {'item': 0, 'name': 'John'}
Flutter now worked with Map<String,String>
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With