Dart contructors

main.dart

void main() {
  Book book = Book(title: 'bookTitle', description: 'bookDescription');
  Book book2 = Book.fromMap({'title': 'Book2', 'description': 'desc2'});
  print(book);
  print(book2);
  
  SuperBook superBook = SuperBook(title: "superBookTitle", description: "superBookDesc", size: 10);
  print(superBook);
  
  Author author1 = Author('fred', 'visticot');
  Author author2 = Author('john', 'smith', '0674639362');
  Author author3 = Author.custom('johsn', 'lorient', tel: '0202020');
  print(author1);
  print(author2);
  print(author3);
  
  print(author1._getName());
 
}

class Author {
  final String firstname;
  final String lastname;
  final String tel;
  final String email;
  
  String _getName() {
    return 'fred';
  }
  
  Author(this.firstname, this.lastname, [this.tel, this.email]);
  
  Author.custom(this.firstname, this.lastname, {this.tel, this.email});
  
  String toString() {
    return '$firstname, $lastname, $email, $tel';
  }
}

class Book {
  final String title;
  final String description;
  
  Book({this.title, this.description});
  
  factory Book.fromCache(Map<String, dynamic> map) {
    return Book(title: map['title'], description: map['description']);
  }
  
   Book.fromMap(Map<String, dynamic> map) : this.title= map['title'], this.description=map['description'];
  
  @override
  String toString() {
    return '$title, $description';
  }
}

class SuperBook extends Book {
  final int size;
  
  SuperBook({String title, String description, this.size}): super(title: title, description: description);
  
  @override
  String toString() {
    return '$title, $description $size';
  }
  
}