I have a code like this:

  //...
  child: ListTile(
    leading: CircleAvatar(
      backgroundImage: NetworkImage("${snapshot.data!.docs[index].data()['urunFotografi']}"),
    ),
    title: Text(snapshot.data!.docs[index].data()["urunAdi"], style: TextStyle(fontSize: 20),),
    subtitle: Text(adetVeyaKilo().toString(), style: TextStyle(fontSize: 15),),
  ),
  // ...

// ...
Future<String> adetVeyaKilo() async {
  String state = "";
    FirebaseFirestore.instance.collection('bolatAktar').where('urunAdi', isEqualTo: urunAdi).get().then((value) {
    value.docs.forEach((element) {
      if (element.data()["urunBirimi"] == "Adet") {
        state = "Adet";
      }
      if (element.data()["urunBirimi"] == "Kilo") {
        state = "Kilo";
      }
    });
  });
  return state;
}
// ...

With the codes I wrote, I am trying to make a return according to the data coming from Firebase Firestore.

But when trying to print to subTitle it prints like this: Instance of Future<String>

Why does this problem occur? How can I solve it?

Thanks in advance for your help.

CodePudding user response：

Try this:

Future<String> adetVeyaKilo() async {
  String state = "";
  await FirebaseFirestore.instance.collection('bolatAktar').where('urunAdi', isEqualTo: urunAdi).get().then((value) {
    value.docs.forEach((element) {
      if (element.data()["urunBirimi"] == "Adet") {
        setState((){
          state = "Adet";
        });
      }
      if (element.data()["urunBirimi"] == "Kilo") {
        setState((){
          state = "Kilo";
        });
      }
    });

CodePudding user response：

You need to write await before FirebaseFirestore.instance.collection('bolatAktar')....

Or you can do like this. This one is better

    final response = await FirebaseFirestore.instance.collection('bolatAktar').where('urunAdi', isEqualTo: urunAdi).get();
for(int i=0;i<response.docs.length;i  ){
if(response.docs[i].data()["urunBirimi"] == "Adet"){
state = "Adet"
}
if(response.docs[i].data()["urunBirimi"] == "Kilo"){
state = "Kilo";
}
}