add optional and named parameters dart constructore code example

Example 1: 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;
  }
}

Example 2: constructor flutter

class Student{
  Student(int enNum){
    print(enNum);
  }
}

main(){
  var myStudent = new Student(15);
}