Switch expression in dart
Source: Nagaraj Alagusundaram
Traditional Switch
In Dart, the switch statement is a control flow statement that lets a variable be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each case.
Traditionally, the syntax of switch statements includes case keywords followed by the possible values and a colon, with a break keyword to exit the case once the code block has been executed.
Example
void main() {
var grade = 'A';
print(evaluateGrade(grade));
}
String evaluateGrade(String grade) {
switch (grade) {
case 'A':
return "Excellent!";
case 'B':
return "Good job!";
case 'C':
return "Work harder!";
default:
return "Invalid grade.";
}
}
Output:
Excellent!Explanation
In this example, the evaluateGrade function takes a grade as input, checks it with a switch statement, and returns a different message depending on the grade. If you run the main function with ‘A’ as the grade, it will print "Excellent!" to the console.
Switch Expression
Dart has introduced a new way of writing switch statements that are more concise and intuitive. This is known as the switch expression. Here’s how you can rewrite the above code using a switch expression:
void main() {
var grade = 'A';
final result = switch (grade) {
'A' => "Excellent!",
'B' => "Good job!",
'C' => "Work harder!",
_ => "Invalid grade."
};
print(result);
}
Output:
Excellent!In this new approach, you can assign the result of the switch expression directly to a variable. The underscore _ acts as a catch-all case, equivalent to the default keyword in traditional switch statements.
This new way of writing switch expressions in Dart makes the code cleaner and more readable, especially when dealing with a large number of cases.