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Flutter – "Then" is not working to fetch data from async and await

I have an async class that fetch token from Flutter Secure Storage

  readSecureData(String key) async {
    String? data = await storage.read(key: key);
    print('data from secure storage: $data');
    return "asdasd";
  }

and I fetch the token with then method and store it in a variable token through a dio factory class as follows

class DioFactory {
  //not to have instance
  // ApiService._();
  final FlutterSecureStorage storage = const FlutterSecureStorage();

          static Dio? dio;
    
      Dio getDio() {
        if (dio == null) {
          String? token = "";

     SecureStorage()
          .readSecureData("login_token")
          .then((value) => token = value);

      print("----------------dio");
      print(token);
      print("----------------dio");

      var headers = {
        'Authorization': "Bearer ${token ?? ''}"
      };

      BaseOptions options = BaseOptions(
        baseUrl: ApiConst.apiBaseUrl,
        headers: headers,
      );

      dio = Dio(options);
      return dio!;
    } else {
      return dio!;
    }
  }

but the token is always returned empty although there is a token and I can see the token is printed in readSecureData function, so how can i fetch the token from readSecureData and store it in the token to send it it the dio header

Tags:

2

Answers


  1. 0 
      void anyFunction() {
    String? anyValue;
    Future.delayed(Durations.long1, () {
      return 'anyString';
    }).then((value) {
      anyValue = value;
    });

    print(anyValue);
  }

    Look, here is a function that contains an async operation but is not defined as Future.

    The output of this function is as follows:

    flutter: null

    Because the assignment process takes place without waiting for the Future.delay process.

    This is a function defined as Future and it does the same job.

      Future<void> anyFunction() async {
    String? anyValue;
    await Future.delayed(Durations.long1, () {
      return 'anyString';
    }).then((value) {
      anyValue = value;
    });

    print(anyValue);
  }

    And here this output:

    flutter: anyString

    Did you understand ?

    You have use this way :

     Future<Dio> getDio() async{
        if (dio == null) {
          String? token = "";

   await  SecureStorage()
          .readSecureData("login_token")
          .then((value) => token = value);

      print("----------------dio");
      print(token);
      print("----------------dio");

      var headers = {
        'Authorization': "Bearer ${token ?? ''}"
      };

      BaseOptions options = BaseOptions(
        baseUrl: ApiConst.apiBaseUrl,
        headers: headers,
      );

      dio = Dio(options);
      return dio!;
    } else {
      return dio!;
    }
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  2. 0

    Future<String>: This function returns a Future that resolves to a String. This indicates that the operation is asynchronous, and when the data is ready, it will be a string.

    async: This keyword is used to mark the function as asynchronous, allowing the use of await inside the function.

    So, first, add Future<String> before readSecureData() method.

      Fture<String> readSecureData(String key) async {
    String? data = await storage.read(key: key);
    print('data from secure storage: $data');
    return "asdasd";
  }

    And then get data from readSecureData() using the following snippets.

    String token = await SecureStorage()
          .readSecureData("login_token");
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