Step 1 - Getter

class Circle {
  double radius;

  Circle(this.radius);

  double get area => 3.14159 * radius * radius;
}

void main() {
  Circle c = Circle(2);
  print(c.area);
}

• get area looks like a property but runs code each time it is read.

Step 2 - Setter with validation

class Temperature {
  double _celsius = 0;

  double get celsius => _celsius;

  set celsius(double value) {
    if (value < -273.15) {
      throw ArgumentError('Too cold');
    }
    _celsius = value;
  }
}

void main() {
  Temperature t = Temperature();
  t.celsius = 20;
  print(t.celsius);
}

• Setters are for when assignment should run checks or side effects.

Step 3 - Prefer simple fields first

• If there is no extra logic, use a normal field (or final when it never changes).
• Add getters/setters when you need computation, validation, or a stable API while internals change.

Good habit

• Do not add getters/setters “just in case”; YAGNI applies.

Practice tasks

• Add a Rectangle with width and height and a getter perimeter.
• Add a Username class that stores _value and rejects empty strings in the setter.
• Replace a redundant getX/setX pair with a public final field if nothing special happens on read/write.