Future<Map<String, dynamic>> Type issue when using a function-CodePudding

I have a call I am making to my Firebase db to return a document to get data from:

                        final docRef = db
                            .collection("GearLockerItems")
                            .doc(itemIDList[index]);
                        var doc = await docRef.get();
                        final data = doc.data() as Map<String, dynamic>;

                        String itemWeight = data['itemWeight'];
                        String itemWeightFormat = data['itemWeightFormat'];

After testing the code and knowing that it works, I wanted to create a function in order to clean up the code and make it easier to read. The function I created looks like this:

Future<Map<String, dynamic>> getItem(
    itemIDList, index) async {
  final docRef = db.collection("Items").doc(itemIDList[index]);
  var doc = await docRef.get();
  final data = doc.data() as Map<String, dynamic>;

  return data;
}

And then I call the function back in my main code with:

Future<Map<String, dynamic>> data = getGearLockerItemInStream(itemIDList, index);

But then when I try and use data as I did earlier to get the individual values like this:

String itemWeight = data['itemWeight'];
String itemWeightFormat = data['itemWeightFormat'];

I know get this error:

The operator '[]' isn't defined for the type 'Future<Map<String, dynamic>>'.
Try defining the operator '[]'

I think the issue is with my types. I struggled on what type I was returning here in the function as I had never used as Map<String, dynamic>; before. The as concept was new to me. Its type casting I believe so I tried to use that type for the function but then struggled in the main code on the type for the data variable.

CodePudding user response：

At first you should await for result because getItem is a async function, so change this:

await getGearLockerItemInStream(itemIDList, index);

because you do await the result wont be a Future anymore so you need to change data type to Map<String, dynamic>>, so your final changes should be like this:

Map<String, dynamic> data = await getGearLockerItemInStream(itemIDList, index);