Instance of 'Future<String>' instead of showing the value

Question

Iam using flutter and I am trying to get a value from shared_preferences that I had set before, and display it in a text widget. but i get Instance of Future<String> instead of the value. here is my code:

Future<String> getPhone() async {
    final SharedPreferences prefs = await SharedPreferences.getInstance();
    final String patientPhone = prefs.getString('patientPhone').toString();
        print(patientPhone);

    return patientPhone;
  }

Future<String> phoneOfPatient = getPhone();

Center(child: Text('${phoneOfPatient}'),))

Hix

Answer 1

There is await missing before prefs.getString( and use setState() instead of returning the value. build() can't use await.

  String _patientPhone;

  Future<void> getPhone() async {
    final SharedPreferences prefs = await SharedPreferences.getInstance();
    final String patientPhone = await /*added */ prefs.getString('patientPhone');
    print(patientPhone);

    setState(() => _patientPhone = patientPhone);
  }

  build() {
    ...
    Center(child: _patientPhone != null ? Text('${_patientPhone}') : Container(),))
  }

Buonaparte

I am not getting that error but the value that is shown is null and I am sure that it is not null because I am using it in another file(that file is a http response and does not have a builder) – Hix

Did you use my _patientPhone != null ... code? The value will be null at first because the code to get it is async and will only result in a value != null after a while. When Flutter runs build() in the meantime, the value will still be null. – Gnatcatcher

Does print(patientPhone); ever print anything? – Gnatcatcher

in other files it does, but here it does not. – Hix

also here with the previous codes it did show the phone, but when I changed it to ur code, it does not print anything – Hix

Try without await /*added */. It seems it is not required here. Instance of 'Future<String>' seems to be coming from another part of your cod. – Gnatcatcher

If there is no phone number stored under this key, then you don't get one. I can't know from the provided information. – Gnatcatcher

no there is a phone, because i am using it to receive response from the server and i am getting the response, also it gets printed in other files – Hix

Everything is possible but I can't verify from here and depend on information you provide. If there were a phone print(patientPhone); would print it though. – Gnatcatcher

github.com/mojtabaparvar/myapp this is my code on github . you can take a look at it – Hix

Answer 2

If you don't have the option to use await or async you can do the following.

getPhone().then((value){
 print(value);
});

and then assign a variable to them. From that, you'll have the result from the value.

Gorizia

Please how can i set the value, mine is only active inside the function not outside, – Rhodie