Chapter 09 — Constructors and Modeling

Level: beginner / intermediate Estimated time: 7 h Prerequisites: chapter 08 — Introduction to OOP (class, object, property, method, this) What you will be able to do by the end: create complete, valid objects from the very first line of their life with constructors, expose computed values with getters, and translate a written description in French into a coherent set of classes.

09.0 — Chapter Objectives

By the end of this chapter, you will be able to:

• explain precisely why a class without a constructor is a problem;
• recognize and use the default constructor;
• write a custom constructor;
• use the this.property shorthand syntax;
• use named parameters with curly braces { };
• make a named parameter mandatory with required;
• declare optional parameters and give them a default value;
• write named constructors such as Player.debutant() or Enemy.boss();
• initialize a property with an initializer list : x = ...;
• protect your objects with assert;
• write a const constructor and explain what it provides;
• write a factory constructor and explain when it is useful;
• write a getter, a setter, and computed getters;
• override toString() to display a readable object;
• turn a written description in French into a set of Dart classes;
• apply a list of modeling best practices.