Using a factory constructor

Dart gives us many flexible and succinct ways to build objects through constructors:

• With optional arguments, such as in the Person constructor where salary is optional:

  class Person{
    String name;
    num salary
    Person(this.name, {this.salary});
  } 

• With named constructors (a bonus for readable self-documenting code), for example, where a BankAccount for the same owner as acc is created:

  BankAccount.sameOwner(BankAccount acc): owner = acc.owner;

• With const constructors, as shown in the following code:

  class ImmutableSquare {
  finalnum length;
  static finalImmutableSquare ONE = const ImmutableSquare(1);
  constImmutableSquare(this.length);
  }

However, modern modular software applications require more flexible ways to build and return objects, often extracted into a factory design pattern (for more information, refer to http://en.wikipedia.org/wiki/Factory_(object-oriented_programming)). Dart has this pattern built right into the language with factory constructors.

How to do...