Impara switch-case Statement in Dart | Conditional Statements

When there are many conditions to check, using multiple if-else statements can become inconvenient.

In this example, the code checks the value of the dayOfWeek variable and prints a message for the matching day. If it’s one of the weekdays, it prints the day’s name; otherwise, it prints "Weekend".

main.dart


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void main() {
  String dayOfWeek = "Friday";

  if (dayOfWeek == "Monday")
  {
    print("Today is Monday.");
  }
  else if (dayOfWeek == "Tuesday")
  {
    print("Today is Tuesday.");
  }
  else if (dayOfWeek == "Wednesday")
  {
    print("Today is Wednesday.");
  }
  else if (dayOfWeek == "Thursday")
  {
    print("Today is Thursday.");
  }
  else if (dayOfWeek == "Friday")
  {
    print("Today is Friday.");
  }
  else
  {
    print("Weekend");
  }
}

The code may look confusing, but it can be made more readable using a switch-case statement. A switch-case statement includes several parts: the switch keyword, multiple case options to compare values, and an optional default block that runs if no case matches.

main.dart


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switch(expresion) {
  case value_1: 
  // code to be executed
  case value_2: 
  // code to be executed
  .............
  default: // code to be executed if all cases are not matched
}

switch(expression): evaluates the value of expression;
case value_1: if expression equals value_1, the corresponding code runs;
default: executes if none of the case values match.

A switch-case statement is a construct that allows you to execute a block of code based on the value of a variable. The variable is called the switch variable. The switch variable is evaluated once, and the corresponding block of code is executed.

main.dart


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void main() {
  String dayOfWeek = "Monday";

  switch (dayOfWeek) {
    case "Monday":
      print("Today is Monday.");
      
    case "Tuesday":
      print("Today is Tuesday.");
      
    case "Wednesday":
      print("Today is Wednesday.");
      
    case "Thursday":
      print("Today is Thursday.");
      
    case "Friday":
      print("Today is Friday.");
      
    default:
      print("Weekend");
  }
}

In this example, the switch variable is dayOfWeek. It’s evaluated once, and the matching code block runs.
Once a matching case executes, the remaining cases are skipped.
If dayOfWeek doesn’t match any case, the default block runs, in this case, it prints "Weekend".

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Sezione 3. Capitolo 4

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When there are many conditions to check, using multiple if-else statements can become inconvenient.

main.dart


              12345678910111213141516171819202122232425262728
            
void main() {
  String dayOfWeek = "Friday";

  if (dayOfWeek == "Monday")
  {
    print("Today is Monday.");
  }
  else if (dayOfWeek == "Tuesday")
  {
    print("Today is Tuesday.");
  }
  else if (dayOfWeek == "Wednesday")
  {
    print("Today is Wednesday.");
  }
  else if (dayOfWeek == "Thursday")
  {
    print("Today is Thursday.");
  }
  else if (dayOfWeek == "Friday")
  {
    print("Today is Friday.");
  }
  else
  {
    print("Weekend");
  }
}

main.dart


              12345678
            
switch(expresion) {
  case value_1: 
  // code to be executed
  case value_2: 
  // code to be executed
  .............
  default: // code to be executed if all cases are not matched
}

switch(expression): evaluates the value of expression;
case value_1: if expression equals value_1, the corresponding code runs;
default: executes if none of the case values match.

main.dart


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void main() {
  String dayOfWeek = "Monday";

  switch (dayOfWeek) {
    case "Monday":
      print("Today is Monday.");
      
    case "Tuesday":
      print("Today is Tuesday.");
      
    case "Wednesday":
      print("Today is Wednesday.");
      
    case "Thursday":
      print("Today is Thursday.");
      
    case "Friday":
      print("Today is Friday.");
      
    default:
      print("Weekend");
  }
}

In this example, the switch variable is dayOfWeek. It’s evaluated once, and the matching code block runs.
Once a matching case executes, the remaining cases are skipped.
If dayOfWeek doesn’t match any case, the default block runs, in this case, it prints "Weekend".

Tutto è chiaro?

Grazie per i tuoi commenti!

Sezione 3. Capitolo 4