Instance variables

Here’s how you declare instance variables:

class Point {
  num x; // Declare instance variable x, initially null.
  num y; // Declare y, initially null.
  num z = 0; // Declare z, initially 0.
}

All uninitialized instance variables have the value null.

All instance variables generate an implicit getter method. Non-finalinstance variables also generate an implicit setter method. For details,see Getters and setters.

class Point {
  num x;
  num y;
}
void main() {
  var point = Point();
  point.x = 4; // Use the setter method for x.
  assert(point.x == 4); // Use the getter method for x.
  assert(point.y == null); // Values default to null.
}

If you initialize an instance variable where it is declared (instead ofin a constructor or method), the value is set when the instance iscreated, which is before the constructor and its initializer listexecute.