How do I return error from a Future in dart?

Throwing an error/exception:

You can use either return or throw to throw an error or an exception.

• Using return:

  Future<void> foo() async {
    if (someCondition) {
      return Future.error('FooError');
    }
  }
  

• Using throw:

  Future<void> bar() async {
    if (someCondition) {
      throw Exception('BarException');
    }
  }
  

---

Catching the error/exception:

You can use either catchError or try-catch block to catch the error or the exception.

• Using catchError:

  foo().catchError(print);
  

• Using try-catch:

  try {
    await bar();
  } catch (e) {
    print(e);
  }
  

You can return the error data like this if you want to read the error object:

response = await dio.post(endPoint, data: data).catchError((error) {
  return error.response;
});
return response;

You can use throw :

Future<List> getEvents(String customerID) async {
  var response = await http.get(
    Uri.encodeFull(...)
  );

  if (response.statusCode == 200){
    return jsonDecode(response.body);
  }else{
    // I want to return error here 
       throw("some arbitrary error"); // error thrown
  }
}