Constant Variables

Part of the Fundamentals section of Coddy's Dart journey — lesson 12 of 94.

The const keyword creates variables with fixed values. When using const, values must be known when writing your code.

void main() {
  const String language = 'Dart';
  print(language);
}

Type inference works with const:

void main() {
  const language = 'Dart';      // String
  const version = 2;            // int
  const isStable = true;        // bool
  const rating = 4.9;           // double
  
  print(language);  // Outputs: Dart
  print(version);   // Outputs: 2
  print(isStable);  // Outputs: true
  print(rating);    // Outputs: 4.9
}

Challenge

Beginner

Create a Dart program that uses constant variables to store information about a fictional planet:

Declare a const String variable named planetName with the value "Mars"
Declare a const int variable named numberOfMoons with the value 2
Declare a const double variable named distanceFromSun with the value 227.9 (in million km)
Declare a const bool variable named hasRings with the value false
Print each variable with a descriptive label exactly as shown in the expected output below:

Planet Name: Mars
Number of Moons: 2
Distance from Sun: 227.9 million km
Has Rings: false

Your output must match this exact format.

Cheat sheet

The const keyword creates variables with fixed values that must be known at compile time:

const String language = 'Dart';
const version = 2;            // Type inference works
const isStable = true;        // bool
const rating = 4.9;           // double

Use const for values that never change during program execution.

Try it yourself

void main() {
  // Declare your const variables here
  const String planetName = ?;
  const int numberOfMoons = ?;
  const double distanceFromSun = ?;
  const bool hasRings = ?;
  
  // Print the variables with labels
  print("Planet Name: $planetName");
  print("Number of Moons: $numberOfMoons");
  print("Distance from Sun: $distanceFromSun million km");
  print("Has Rings: $hasRings");
}