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Summary - Conditionals

Combine if, switch and pattern matching to write a day-of-week app.

Summary - Conditionals

In this group you learned if, else, switch, the Dart 3 switch expression and the ternary. Now we will combine them to write a day-of-week application.

The app will produce a day name from an integer 1-7. A switch expression is the most fitting structure for matching several values; the _ wildcard catches unexpected values. The goal is to use the right structure in the right place.

Plan

We will build the app step by step: (1) give the int day variable a value; (2) assign the switch (day) expression to the name variable; (3) write a => arm for each number; (4) catch unexpected values with the _ wildcard; (5) print with print(name);.

This structure is the core of a real calendar app too. Turning a number from the user into a day name is common in screen flows. The _ arm lets you catch wrong input gracefully.

Practice Day-of-week app

Declare an int variable day with the value 3. Declare a variable name and assign it to a switch (day) expression: arms 1 => "Monday", 2 => "Tuesday", 3 => "Wednesday", _ => "Unknown". Then print name with print(name);. The output on a single line must be Wednesday.

Starter code

main.dart
// Declare day, assign the day name to name with a switch expression, print it

Sample solution

main.dart
int day = 3;
var name = switch (day) {
  1 => "Monday",
  2 => "Tuesday",
  3 => "Wednesday",
  _ => "Unknown",
};
print(name);

Expected output

Wednesday

Questions and answers

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

1 Which structure best fits turning 1-7 into a day name?

main.dart
int day = 3;
  • if/else chain
  • while loop
  • for loop
  • switch expression Correct answer

Explanation: switch expression is the most readable for multi-value matching.

2 Complete the wildcard arm

Question 
var name = switch (day) {
  1 => "Monday",
  2 => "Tuesday",
  3 => "Wednesday",
  ____ => "Unknown",
};
Answer 
var name = switch (day) {
  1 => "Monday",
  2 => "Tuesday",
  3 => "Wednesday",
  _ => "Unknown",
};

Explanation: _ is the wildcard meaning 'everything else'.

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