CodeBlanks Logo Icon CodeBlanks
Login Register

switch

Learn multi-way selection with switch, case, break and default.

switch

To check many values of a variable in order you use switch. In switch (day) { case "Mon": ...; break; default: ...; } the matching case runs based on the value of day.

switch is a more readable form of many else ifs. case values must be constants; they cannot be variables. If no case matches default runs; default is optional but a good habit.

break and default

At the end of each case block break; exits the switch; otherwise Dart gives an error. break is a separate concept; you will see more about it with loops in the next section. For now know it exits the switch.

The default block runs when no case matches. It is the switch equivalent of else. default is usually written last but is not required. Practical tip: give every switch a default to catch unexpected values.

Practice Day name with switch

Declare a String variable day with the value "Mon". With switch (day): in the case "Mon": block print print("Monday"); and exit with break;. In the default: block print print("Unknown");. The output on a single line must be Monday.

Starter code

main.dart
// Declare day, switch Mon to Monday and print it

Sample solution

main.dart
String day = "Mon";
switch (day) {
  case "Mon":
    print("Monday");
    break;
  default:
    print("Unknown");
}

Expected output

Monday

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Match each part to its job

Term Meaning
switch (x) Variable to check
case A: A value match
default: When none match
break; Exits the switch

2 Write the case line

Question 
String day = "Mon";
switch (day) {
  case ____:
    print("Monday");
    break;
  default:
    print("Unknown");
}
Answer 
String day = "Mon";
switch (day) {
  case "Mon":
    print("Monday");
    break;
  default:
    print("Unknown");
}

Explanation: case "Mon": is the form; no parentheses, square or curly brackets needed.

3 What runs if no case matches in a switch?

main.dart
switch (x) {
  case 1: ...; break;
  default: ...;
}
  • the default block Correct answer
  • The program crashes
  • The first case runs again
  • Nothing at all

Explanation: The default block runs when no case matches.

All lessons in Beginner

1 Dart basics

  1. What is Dart?
  2. Your first program
  3. dart run
  4. Comments
  5. String interpolation
  6. Summary - Dart basics

2 Variables

  1. var and type
  2. final
  3. const
  4. late
  5. Null safety
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. bool and String
  4. Type inference
  5. dynamic
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Null-aware operators
  6. Summary - Operators

6 Strings

  1. Creating strings
  2. String interpolation
  3. length and methods
  4. substring
  5. contains and indexOf
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. switch
  4. Pattern matching
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. for-in
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Lists

  1. Creating lists
  2. List access
  3. add and remove
  4. length and contains
  5. List methods
  6. Summary - Lists

11 Sets and Maps

  1. Set
  2. Set operations
  3. Map
  4. Map operations
  5. Map iteration
  6. Summary - Sets and Maps

12 Functions

  1. Defining functions
  2. Return values
  3. Arrow functions
  4. Optional parameters
  5. First-class functions
  6. Summary - Functions

13 Null safety in depth

  1. Nullable types
  2. Null-aware operators
  3. The ! operator
  4. late
  5. Null check
  6. Summary - Null safety

14 Class basics

  1. class
  2. Constructor
  3. Instance variables
  4. Methods
  5. this
  6. Summary - Class basics

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. split and join
  2. replace
  3. trim and pad
  4. RegExp
  5. StringBuffer
  6. Summary - Advanced strings

17 Enums

  1. Defining enums
  2. Enum values
  3. Enhanced enums
  4. switch with enum
  5. Enum and patterns
  6. Summary - Enums

18 Exceptions

  1. try/catch
  2. throw
  3. finally
  4. The Exception class
  5. on clause
  6. Summary - Exceptions

19 Async basics

  1. Future
  2. async/await
  3. then
  4. Future.error
  5. Future.wait
  6. Summary - Async basics

20 Beginner final

  1. Project design
  2. Classes
  3. Collections
  4. Error handling
  5. Putting it together