basic_types.dart

void main() {
  
  // ---------- 1- numbers
  int counter; // null
  double priceEach; // null
  
  int counter1 = 0;
  double texRate = 20;
  
  num counter2 = 10; // int
  num price = 14.16; // double
  
  int? age = int.tryParse("25"); // parse a string to int
  
   // ---------- 2- strings
  String student1 = "Emna";
  
  //parsing to string
  int age2 = 19;
  String stringAge = age2.toString();
  
  //string operations
  String country = "Tunisia";
  print(country.toUpperCase());
  print(country.toLowerCase());
  print(country.substring(0, 3));
  
  // ---------- 3- dynamic types
  var phone = "(+216)22334455";
  print(phone.runtimeType);
  // phone = 22334455; // error: value type int can't be assigned to variable type string
  
  dynamic id = "user12345";
  print(id.runtimeType); // String
  
  id = 12345;
  print(id.runtimeType); // int
  
  // ---------- 4- constants
  final double taxRate2 = 20;
  //taxRate2 = 19; // error: final variable can be only set once
  
  final List<int> tab = [12, 73, 55];
  tab.add(38);
  print(tab);
  
  const List<int> tab2 = [12, 73, 55];
  //tab2.add(38); // error : unsupported operation
  
   // ---------- 5- collections
   // 1. list
  List<int> numbers = [];
  numbers.add(34);
  numbers.add(76);
  numbers.add(50);
  numbers.add(312);
  numbers.add(47);
  print(numbers);
  
  // clear() : remove array content
  // numbers.clear();
  // print(numbers);
  
  // indexOf(element) : first index of element in the list.
  print(numbers.indexOf(50)); // 2
  print(numbers.indexOf(55)); // -1
  
  // remove(value) : removes the first occurence of value
  numbers.remove(50);
  print(numbers);

  //removeAt(index) : removes value at position index
  //numbers.removeAt(1);
  //print(numbers);
  
  // removeLast() remove the value at the last position
  //int elem = numbers.removeLast();
  //print(elem);
  //print(numbers);
  
  // length
  print(numbers.length);
  
  numbers.sort();
  print(numbers);
  
  // 2. Maps
  
  // declaration 1
  var student = Map();
  student['name'] = "Jasser";
  student['age'] = 20;
  print(student);
  
  // declaration 2
  var student2 = {'name': "Emna", 'address': "Tunis"};
  print(student2);
  
  // values
  print(student['name']);
  print(student2.values);
    
}

functions.dart

void main() {
  // simple function
  sayHello();
  
  // function with return
  String message = getMessage();
  print(message);
  // or
  print(getMessage());
  
  // function with params
  print(getMessage2("Mahmoud"));
  
  // function with optional params
  print(getMessage3("Emna"));
  print(getMessage3("Emna", "Mrs"));
  
  // anonymous function
  const fruits = ['apples', 'bananas', 'oranges'];
  fruits.forEach((fruit) {
    print('${fruits.indexOf(fruit)}: $fruit');
  });
}

// simple function
void sayHello() {
  print('Hello Dart!');
}

// function with return
String getMessage() {
  String message = "Hello Dart!";
  return message;
}

// function with params
String getMessage2(String username) {
  return "Hello ${username.toUpperCase()}";
}


// function with optional params
String getMessage3(String username, [String? title]) {
  String message;
  if(title == null) {
    message ="Hello ${username.toUpperCase()}";
  } else {
    message = "Hello $title ${username.toUpperCase()}";
  }
  
  return message;
}

// arrow functions / lambda functions
String getMessage4(String username) {
  return "Hello ${username.toUpperCase()}";
}

String getMessage5(String username) => "Hello ${username.toUpperCase()}";