Dart Basics

Every Dart program starts in a function called main. print writes a line to the console, which is handy while you learn.

void main() {
  print('Hello, Dart!');
}

Variables and types

• var lets Dart work out the type: var city = 'Phnom Penh'; is a String.
• final is set once and never changes. Use it for most values.
• const is a value that is known before the app runs, like const pi = 3.14;.
• Common types: int (whole numbers), double (decimals), String (text) and bool (true or false).

final String name = 'Dara';
int score = 8;
score = score + 1; // allowed: score is not final
const bool isBeginner = true;

Putting values into text

Write $name inside a string to insert a variable, or ${...} for an expression, like ${score * 10}. This is called string interpolation.

Functions

A function lists its return type, its name and its parameters. When the body is a single expression you can use the short arrow form =>.

int add(int a, int b) {
  return a + b;
}

String greet(String name) => 'Hello, $name!';

Null safety

A normal variable can never be null. Add ? to the type when a value may be missing, and use ?? to give a fallback.