Dart Null Safety

 class Ivan{

  String? name;

  int? age;

}

class Aprivate{

  String? name, surename;

  int? _age;

  

  void set age(int years) {

    if(years > 0 && years < 120) {

      _age = years;

      

    }else {

      _age = 0;

    }

  }

  int get age {

     return _age!; // to return null adding ! at the end

  } 

   

}

void main() {

  Aprivate another = Aprivate();

  another.name = 'Lert Ivan';

  another.surename = 'Ivan Boginski';

  another.age = 22;

  print('name: ${another.name} \n surename: ${another.surename} \n age: ${another.age}');

  

  

  Ivan tel = Ivan();

  tel.name = 'Ivan Boginski';

  tel.age = 27;

  print('Name: ${tel.name}\n Age: ${tel.age}');

  

  

  String myString = 'Throw your Dart';

  String result = reverse(myString);

  print(result);

  String mySongs = anohterSing();

  print(mySongs);

}

String reverse(String young) {

  int length = young.length;

  String res = '';

//   String? res;

  for (int i = length-1; i >= 0; i--) {

   res += young.substring(i,i + 1); 

  }

  return res;

}

// String sing() {

// var songs = <String>[];

// var songString = '';

// // var String? songString;

// songs.add('I think is better');

// songs.add('This');

// songs.add('Nothing bad');

// int i = 0;

// // while ( i < songs.length) {

// // songString += '${songs[i]} - ';

//   songs.forEach((song) => songString += song + " - ");

// i++;

// }

// return songString;

// }

String anohterSing() {

  var songs = <String>[];

  songs.add('Nothing  Crazy');

  songs.add('Yeah');

  songs.add('There is yours');

  var capitalSongs = songs.map((song) => song.toUpperCase());

  return capitalSongs.toString();

}