Switch

1. Switch Flow Control

The switch statement allows us to replace several nested if-else constructs and thus improve the readability of our code.


2. Syntax :



switch(variable_expression) {
   case constant_expr1: {
       // statements;
   }
   break;
   
   case constant_expr2: {
       //statements;
   }
   break;
   
   default: {
       //statements;
   }
   break;
}




3. Example

Let's say, we have the following nested if-else statements:




import 'dart:io';

 

void main() {

  print("enter +,-,*,%");

  String oper = stdin.readLineSync();

  int x = 15, y = 7, result;

  if (oper == "+") {

    result = x + y;

  } else if (oper == "-") {

    result = x - y;

  } else if (oper == "*") {

    result = x * y;

  } else if (oper == "%") {

    result = x % y;

  } else

    print("Error");

  print("result = $result");

}





enter +,-,*,%
*
result = 105



enter +,-,*,%
/
Error
result = null




With switch case statement, the code become like that :




import 'dart:io';

 

void main() {

  print("enter +,-,*,%");

  String oper = stdin.readLineSync();

  int x = 15, y = 7, result;

  switch (oper) {

    case "+":

      {

        result = x + y;

      }

      break;

    case "-":

      {

        result = x - y;

      }

      break;

    case "*":

      {

        result = x * y;

      }

      break;

    case "%":

      {

        result = x % y;

      }

      break;

    default:

      {

        print("Error");

      }

      break;

  }

  print("result = $result");

}





enter +,-,*,%
%
result = 1



/
Error
result = null