how to make defalut constructor in dart code example

Example: dart call constructor in constructor

class Chipmunk {
  String name;
  int fame;

  Chipmunk.named(this.name, [this.fame]);

  Chipmunk.famous1() : this.named('Chip', 1000);
  factory Chipmunk.famous2() {
    var result = new Chipmunk.named('Chip');
    result.fame = 1000;
    return result;
  }
}