Dart Switch
Elegant way to handle multiple conditions
🔀 What is Switch Statement?
Switch statements provide a clean way to execute different code blocks based on the value of a variable. It's more readable than multiple if-else statements when checking one variable against many values.
// Simple switch example
void main() {
String day = 'Monday';
switch (day) {
case 'Monday':
print('Start of work week');
break;
case 'Friday':
print('TGIF!');
break;
default:
print('Regular day');
}
}
Switch Statement Features
Case Labels
Define different values to match
case 'value1':
// code here
break;Break Statement
Prevents fall-through to next case
case 'A':
print('Excellent');
break;Default Case
Handles unmatched values
default:
print('No match found');
break;Fall-through
Execute multiple cases together
case 'A':
case 'B':
print('Good grade');
break;🔹 Basic Switch Statement
Compare a variable against multiple values:
void main() {
int dayNumber = 3;
switch (dayNumber) {
case 1:
print('Monday');
break;
case 2:
print('Tuesday');
break;
case 3:
print('Wednesday');
break;
case 4:
print('Thursday');
break;
case 5:
print('Friday');
break;
default:
print('Weekend');
break;
}
}Output:
Wednesday
🔹 Switch with Strings
Switch statements work with strings too:
void main() {
String grade = 'B';
switch (grade) {
case 'A':
print('Excellent! 90-100%');
break;
case 'B':
print('Good! 80-89%');
break;
case 'C':
print('Average! 70-79%');
break;
case 'D':
print('Below Average! 60-69%');
break;
case 'F':
print('Failed! Below 60%');
break;
default:
print('Invalid grade');
break;
}
}Output:
Good! 80-89%
🔹 Fall-through Cases
Multiple cases can share the same code block:
void main() {
String month = 'December';
switch (month) {
case 'December':
case 'January':
case 'February':
print('Winter season');
break;
case 'March':
case 'April':
case 'May':
print('Spring season');
break;
case 'June':
case 'July':
case 'August':
print('Summer season');
break;
case 'September':
case 'October':
case 'November':
print('Autumn season');
break;
default:
print('Invalid month');
break;
}
}Output:
Winter season
🔹 Switch vs If-Else
Compare switch statement with equivalent if-else:
🔸 Using If-Else (longer)
void checkTrafficLight(String color) {
if (color == 'red') {
print('Stop');
} else if (color == 'yellow') {
print('Caution');
} else if (color == 'green') {
print('Go');
} else {
print('Invalid color');
}
}🔸 Using Switch (cleaner)
void checkTrafficLight(String color) {
switch (color) {
case 'red':
print('Stop');
break;
case 'yellow':
print('Caution');
break;
case 'green':
print('Go');
break;
default:
print('Invalid color');
break;
}
}🔹 Switch Best Practices
Follow these guidelines for effective switch statements:
Good Practices:
- Always use break: Prevents accidental fall-through
- Include default case: Handle unexpected values
- Use for exact matches: Switch works with specific values
- Keep cases simple: Complex logic should be in functions
// Good practice example
void processUserInput(String command) {
switch (command.toLowerCase()) {
case 'start':
startApplication();
break;
case 'stop':
stopApplication();
break;
case 'pause':
pauseApplication();
break;
default:
print('Unknown command: $command');
showHelp();
break;
}
}