Flutter/Dart returning Instance of '_Future<String>' instead the actual String Value-CodePudding

Following is my code. I'm trying to return the value of document ID from the Firebase database so I can delete that specific document.

Future<String> getID() async {
    List<String> id = [];

    //Map<String, dynamic> user = jsonDecode(jsonString);
    await FirebaseFirestore.instance.collection("Babies").get().then((event) {
      for (final doc in event.docs) {
        id.add(doc.data()['ID']);
      }
    });

    return id.length > 0 ? id[0] : 'No Id';
  }
}

Here is another code calling the getID().

ElevatedButton(
            style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all(
                    Color.fromARGB(255, 239, 106, 62))),
            child: const Text("Remove Baby"),
            onPressed: () {
              setState(()  {
                DocumentReference _documentReference = FirebaseFirestore
                    .instance
                    .collection('Babies')
                    .doc(getID().toString());

                _documentReference.delete();
                print(getID().toString());
              });
            },
          ),

When running the program, the

print(getID().toString());

returns Instance of '_Future<String>' instead the actual document ID.

CodePudding user response：

since the getId is asynchronous, you will need to await for it until it

returns String, otherwise it will return the type of the method, try this :
     
   onPressed: () async { // add async
              setState(()  {
                DocumentReference _documentReference = FirebaseFirestore
                    .instance
                    .collection('Babies')
                    .doc(getID().toString());

                _documentReference.delete();
                print(await getID()); // add await
              });
            },

CodePudding user response：

Because Future<:String:> returns a Future<:String:>, not a string. You can get this with await;

print(await getID());