Why can't we assign String to stdin?

Question

I'm new at dart. I think that it's about the new dart version that I can't assign String to stdin.readLineSync(). Can Someone Pls tell me the alternatives?

This is just a basic calculator where I'm trying to add two numbers.

import 'dart:io';
import 'dart:math';


void main() {
  print("Enter first number: ");
  String? num1 = stdin.readLineSync();
  print("Enter second number: ");
  String? num2 = stdin.readLineSync();

  print(num1 + num2);

  
}

The linked answer is not exact the same problem but very similar since your problem is not with `int.parse` but with using the `+` operator on a `String?` type. But the answer describes in details the problem you are having with nullable types and the different solutions for that. :) — julemand101, Dec 10 '21 at 05:38

gretal · Answer 1 · 2021-12-10T03:58:35.843

This is the alternative way how you do:

In Dart programming language, you can take standard input from the user through the console via the use of .readLineSync() function.

import 'dart:io';

void main()
   {   
    print("Enter first number");
    int? n1 = int.parse(stdin.readLineSync()!);

    print("Enter second number");
    int? n2 = int.parse(stdin.readLineSync()!); 

    int sum = n1 + n2;
    print("Sum is $sum");
   }

and here it is clearly explained about your problem "The argument type 'String?' can't be assigned to the parameter type 'String'" when using stdin.readLineSync()

Why can't we assign String to stdin?

1 Answers1