The switch statement in Dart is a control flow statement that allows you to execute different blocks of code based on the value of a variable or an expression. It is a more organized way to handle multiple conditions compared to using a series of if-else statements, particularly when you need to evaluate the same variable against different values.

Syntax

The basic syntax of a switch statement is as follows:

switch (expression) {
  case value1:
    // Code to execute if expression equals value1
    break;
  case value2:
    // Code to execute if expression equals value2
    break;
  // You can have any number of case statements
  default:
    // Code to execute if expression matches none of the cases
}

Components of a switch Statement

• Expression: The expression is evaluated once and compared with the values in each case.
• Case Statements: Each case checks if the expression matches a specific value. If it matches, the corresponding block of code is executed.
• Break Statement: The break statement is used to exit the switch block. If you omit the break, execution will "fall through" to the next case.
• Default Case: The default case is optional and is executed if none of the specified cases match the expression.

Example

Here’s a simple example to illustrate how the switch statement works:

void main() {
  String fruit = 'banana';

  switch (fruit) {
    case 'apple':
      print('You chose apple.');
      break;
    case 'banana':
      print('You chose banana.'); // This will be executed
      break;
    case 'orange':
      print('You chose orange.');
      break;
    default:
      print('Unknown fruit.');
  }
}

Fall-Through Behavior

If you do not use a break statement, Dart will continue executing the subsequent case statements until it hits a break or the end of the switch. This is known as "fall-through" behavior.

Example:

void main() {
  int number = 2;

  switch (number) {
    case 1:
      print('Number is 1');
      break;
    case 2:
    case 3:
      print('Number is either 2 or 3'); // This will be executed
      break;
    default:
      print('Number is something else');
  }
}

Using Multiple Cases

You can group multiple cases together if they should execute the same block of code:

void main() {
  int day = 5;

  switch (day) {
    case 1:
    case 2:
    case 3:
    case 4:
    case 5:
      print('It\'s a weekday.'); // This will be executed for days 1 to 5
      break;
    case 6:
    case 7:
      print('It\'s the weekend.');
      break;
    default:
      print('Invalid day.');
  }
}

Important Notes

• Expression Type: The expression used in a switch statement must evaluate to an integer, string, or a compile-time constant expression.
• Performance: In some cases, switch statements can be more efficient than multiple if-else statements, particularly when dealing with many possible conditions.
• Readability: Using a switch statement can make your code easier to read and maintain when you have multiple values to compare against a single variable.

Conclusion

The switch statement is a powerful tool in Dart for handling multiple conditions based on the value of an expression. It enhances code readability and organization, particularly when compared to using multiple if-else statements. By understanding how to use switch, you can effectively control the flow of your Dart applications based on various input values.