Dart design

Learn Dart language design principles.

Dart design

Dart is a language that targets fast compilation, runtime efficiency and developer productivity together. Sound null safety, a static type system and a dual JIT/AOT mode are the result of these goals.

The same source can compile to both web and native platforms. Static checking is the default; dynamic is the escape hatch. These lessons cover the language design decisions and the reasoning behind them.

Static and dynamic balance

Dart's type system is static by default; most errors are caught at compile time. Still, the dynamic type is available when runtime checks are needed.

Object is the supertype of all objects but method calls are checked at compile time. This balance combines safety with flexibility: the safe path is open, and the escape hatch is available. Dart's philosophy is 'safe defaults, flexibility when needed'.

Exercise A Point class with static types

Define a Point class with final int x; and final int y; fields, a Point(this.x, this.y); constructor and an int sum() => x + y; method. In main create final p = Point(3, 4);; print the result with print(p.sum());.

Show example solution

class Point {
  final int x;
  final int y;
  Point(this.x, this.y);
  int sum() => x + y;
}

void main() {
  final p = Point(3, 4);
  print(p.sum());
}

Test yourself

What is one of Dart's design goals?
- No garbage collector
- Sound null safety
- Manual memory management
- Browser only
Show answer

Sound null safety — sound null safety is one of Dart's core design goals.

Assign a value to a String variable

String greeting = ____;
print(greeting);

Show answer

String greeting = 'Hello';
print(greeting);

Match the Dart design parts

Sound null safety

Null reference safety
Static type system

Compile-time checking
AOT compilation

Single binary (native)
JIT compilation

Fast development

Next lesson: Sound null safety

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