[ta-edu-course-survival-game] Chapter 2 — Composition vs Inheritance (1)

_Instructions.md

• Convert Interactable.cs into an abstract class
• Convert Interact() into an abstract method
  • Taking the inheritance approach, our plan will be to have each new interactable inherit from Interactable
• Create InteractableItem.cs
• Make InteractableItem inherit from Interactable
• Implment Interact()
  • If we want the player to be able to interact with items, we need to create a new implementation of Interactable to handle it
• Add a string property called "Item"
• Add an Inventory property called "Inventory"
• Add a call to Inventory.Add(Item) to Interact()
  • We'll keep our initial implementation simple
  • No spaghetti code here, right?
  • But what if we want to reward the player with an achievement when they collect a certain amount of a particular item?
• Add an Achievements field called "Achievements"
• Add a string property called "AchievementIdentifier"
• Add a call to Achievements.Track(AchievementIdentifier)
  • Here's where we run into our first bit of trouble
  • We've just coupled our achievement system to interactable items
  • This may seem small and isolated, but it's likely that other systems or behaviors will eventually need to know when an item has been interacted with

Achievements.cs

public class Achievements : MonoBehaviour
{
  public void Track(string identifier)
  {
    // Track achievememnt progress
  }
}

Interactable.cs

public abstract class Interactable : MonoBehaviour
{
  public abstract void Interact();
}

InteractableItem.cs

public class InteractableItem : Interactable
{
  public Inventory Inventory;
  public string Item;
  public Achievements Achievements;
  public string AchievementIdenifier;

  public void Interact()
  {
    Inventory.Add(Item);
    Achievements.Track(AchievementIdenifier);
  }
}