Dart Basics II

DartBasics2.dart

/*
 * Dart Basics II: 
 * Written By: Kyra Samuel
 * Coded By: Kyra Samuel 
 * Twitter/GitHub/Discord:
 * @modernlabrat
 * Sources: 
 * * * * * * Udemy - Flutter & Dart
 * - The Completed Guide [2020
 * Edition]
 * * * * * * O'Reilly - Programming
 * Flutter
 * * * * * * Introduction to Dart for 
 * Java Developers
 * 
 * DartPad.dev 
 * 
 * Dart doesn't use the keywords
 * public, private, or protected.
 * 
 * Dart supports top-level functions.
 *  
 */

class _APrivateClass {
  
  /* 
   * I am a private class.
   * I am only accessible from within
   * the current package.
  */
}

void main() {
  var a = 4.2e2; // specify powers of 10 by using 'e'
  print('powers of 10: ' + a.toString()); // toString on num subclasses for proper String concatenation
  
  num _privateNum; // a private variable
  _privateNum = 4; 
  
  var fourInt = _privateNum as int; // type casting using the keyword 'as'
  
  /* 
   * type casting is used in Dart
   * to cast a value to one of its
   * subtypes i.e num => int, num
   * => double
  */
  
  print('num to int: ' + fourInt.toString()); // need toString()
  
  List<num>list = [1, 2, 3]; // List of type num
  print('num list: $list');
  
  var numListToInt = list.cast<int>(); // use 'cast' to cast all values of List
  print('numListToInt $numListToInt');
  
  
  var roundMe = 5.6;
  print('roundMe.round(): ' + roundMe.round().toString());
  
  /*
   * The Non-null selector, ??,
   * operator is used to select
   * the non-null value.
   * 
   */
  
  var nonNull = 10; // non-null value
  int nullNull; // null value
  
  var sinceNonNull = nonNull ?? 2; // nonNull has a value of 10, so sinceNonNull has a value of 10.
  
  var sinceNull = nullNull ?? 3; // nullNull has a value of Null, so sinceNull has a value of 3.
  
  print('sinceNonNull: ${sinceNonNull}');
  print('sinceNull: ${sinceNull}');
  
  var aSet = { // A Set is a linear collection of different values.
    'Red',
    'Blue',
    'Green',
    'Purple'
  };
  
  print('aSet: $aSet');
  
  // remove and add elements to a Set
  var set2 = aSet
    ..remove('Red')
    ..add('Yellow'); // note the syntax.
  print('set2: $set2');
}