The operator '[]' isn't defined for the type 'Object' when trying to access data from futureBuilder

user_14897868 0
Viewed 74

im trying to return two futures and getting the above error when trying to access the data within the returned snapshot.Specifically this line:

${snapshot.data!["firstName"]}

Any ideas as to the correct way to access this data, can't see any documentation anywhere defining this.

Code is as follows:

Widget build(BuildContext context) {
    return FutureBuilder(
      future: Future.wait([getData(), getMood()]),
      builder: (_, snapshot) {
        if (snapshot.hasData) {


          return Scaffold(
            appBar: AppBar(
              title: const Text('Display the Picture'),
              backgroundColor: kPrimaryColor,
            ),
            // The image is stored as a file on the device. Use the `Image.file`
            // constructor with the given path to display the image.
            body: Center(
              child: Column(
                children: <Widget>[
                  Padding(
                    padding: const EdgeInsets.fromLTRB(8.0, 20.0, 8.0, 8.0),
                    child: Column(
                      children: [
                        Center(
                          child: Text(
                            "${snapshot.data!["firstName"]} \n\n "
                            "We have predicted your mood as:\n\n "
                            "${snapshot.data!.data()!["mood"]}\n\n"
                            "Please select a reason associated to your mood",
                            style: const TextStyle(
                                color: Colors.black, fontSize: 15),
                            textAlign: TextAlign.center,
                          ),
                        ),
                      ],
                    ),
                  ),
                ],
              ),
            ),
          );
        } else {
          return CircularProgressIndicator();
        }
      },

    );
  }

  Future getData() async {
    var currentUser = FirebaseAuth.instance.currentUser;
   DocumentSnapshot q1 = await FirebaseFirestore.instance
        .collection('USER_TABLE')
        .doc(currentUser!.uid)
        .get();
    return q1;
  }

  Future getMood() async {
    var currentUser = FirebaseAuth.instance.currentUser;
    QuerySnapshot q2 = await FirebaseFirestore.instance
        .collection('userMood')
        .where('userId' == currentUser!.uid)
        .orderBy('createdAt',descending: true)
        .limit(1)
        .get();
    return q2;
  }

}

Thanks

EDIT

future: Future.wait([getData(), getMood()]),
      builder: (BuildContext context, AsyncSnapshot<List> snapshot) {
        if (snapshot.hasData) {
          var a = snapshot.data![0]["firstName"] as String;
          var b = snapshot.data![1]['Prediction'] as String;

Future <String> getData() async {
    var currentUser = FirebaseAuth.instance.currentUser;
   DocumentSnapshot q1 = await FirebaseFirestore.instance
        .collection('USER_TABLE')
        .doc(currentUser!.uid)
        .get();
    return q1.toString();
  }

  Future <String> getMood() async {
    var currentUser = FirebaseAuth.instance.currentUser;
    QuerySnapshot q2 = await FirebaseFirestore.instance
        .collection('userMood')
        .where('userId' == currentUser!.uid)
        .orderBy('createdAt',descending: true)
        .limit(1)
        .get();
    return q2.toString();
  }
firebase flutter
1 Answers

Let's simplify the task:

Future getA() async {
  await Future.delayed(Duration(seconds: 1));
  return 12.34;
}

Future getB() async {
  await Future.delayed(Duration(seconds: 1));
  return 'abc';
}

... FutureBuilder(
  future: Future.wait([getA(), getB()]),
  builder: (context, snapshot) {
    if (snapshot.hasData) {
      // how to get a and b from snapshot?
    } else {
      return CircularProgressIndicator();
    }
  },
)

You're trying to do snapshot.data!['a'] and snapshot.data!['b']. It doesn't work because snapshot.data isn't Map<String, something>.

Future.wait returns Future<List<T>>. So snapshot.data will be List<T>, and you can get individual items like snapshot.data![0] and snapshot.data![1].

Another problem is that Future.wait doesn't support different item types, so the items type will be Object and you'll need to cast it manually.

Future<double> getA() async {
  await Future.delayed(Duration(seconds: 1));
  return 12.34;
}

Future<String> getB() async {
  await Future.delayed(Duration(seconds: 1));
  return 'abc';
}

... FutureBuilder<List<Object>>(
  future: Future.wait([getA(), getB()]),
  builder: (context, snapshot) {
    if (snapshot.hasData) {
      var a = snapshot.data![0] as double;
      var b = snapshot.data![1] as String;
      return Text('$a $b');
    } else {
      return CircularProgressIndicator();
    }
  },
)
user_61316110
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