Inheritance, need advices

Question

Let's say I have an ai or player, I want him to be able to use different weapons. My design with weapons:

public class Weapon()
{
    public virtual void FireWeapon(){} // this is useless for melee weapons
    public virtual void SwingMelee(){} // this is useless for guns
    public virtual void Reload(){} // this is also useless for melee weapons
}

Then in the ai controller class I simply call the function I want him to do. This is where the ugly part is (I think)... Controller class have a list containing some different weapons of ai and a weapon which is being used.

public class WeaponController
{
   private List<Weapon> someWeapons;
   private Weapon aWeapon;
   public void Main()
   {
      if(/*"Some action or a button click" &&*/ aWeapon.CanSwingMelee() )
         aWeapon.SwingMelee(); 
      if(/*"Some action or a button click" &&*/ aWeapon.CanReload() )
         aWeapon.Reload();
   }
}

What is the better way to implement this? do you have any advices? Seems that for every different action in a new weapon, I need to implement a function in the most parent Weapon class and I don't think it's a good idea...

Answer 1

I don't recommend an approach that requires you to create new interfaces for every new behavior and check the type of the weapon. What about something like this:

(This is a very rough draft.)

public abstract class Weapon
{
    protected Weapon(WeaponCommandStrategy[] commandStrategies)
    {
        CommandStrategies = commandStrategies;
    }

    protected IEnumerable<WeaponCommandStrategy> CommandStrategies { get; }

    public void Use(WeaponCommand command)
    {
        var strategy = CommandStrategies.FirstOrDefault(c => c.Command == command);
        strategy?.Execute();
    }
}

public enum WeaponCommand
{
    Fire,
    Swing,
    Reload
}

public abstract class WeaponCommandStrategy
{
    public WeaponCommand Command { get; private set; }

    protected WeaponCommandStrategy(WeaponCommand command)
    {
        Command = command;
    }

    public abstract void Execute();
}

Now you can give a weapon whatever behaviors you want it to have in the form of various instances of WeaponCommandStrategy. If a command is sent to a weapon, it executes it. If it doesn't support a command it ignores it. You could add a property to a weapon exposing the available commands so that you could display a list of available commands.

public class Sword : Weapon
{
    // Perhaps use dependency injection here
    public Sword() 
        : base(new WeaponCommandStrategy[] { new SwordSwingStrategy() })
    {
    }
}

public class SwordSwingStrategy : WeaponCommandStrategy
{
    public SwordSwingStrategy() : base(WeaponCommand.Swing) { }

    public override void Execute()
    {
        // Do whatever it does
    }
}

This essentially makes a Weapon a composition of various things that a weapon can do. If several weapons behave similarly they can share strategies vs. having code duplicated between various weapons.

Answer 2

The capability of an in-game object can be represented by an interface; you can check if a capability is present by attempting to cast to the interface. What's more, these interfaces can overlap, e.g. both melee and ranged weapons might both have an Attack method.

So for example:

public interface IWeapon
{
    void Attack();
}

public interface IRangedWeapon
{
    bool IsInRange(ITargetable target);
}

public interface IRequiresAmmunition
{
    void Reload();
    int  AmmoRemaining { get; set; }
}

public class Sword : IWeapon
{
    public virtual void Attack() { //code }
}

public class Rifle : IWeapon, IRequiresAmmunition, IRangedWeapon
{
    public virtual void Attack() { //code }
    public virtual void Reload() { //code }
    public virtual int  AmmoRemaining { get { } set { } }
    public virtual bool IsInrange (ITargetable target) { //code }
}

public class LaserGun: IWeapon, IRangedWeapon
{
    public virtual void Attack() { //code }
    public virtual bool IsInrange (ITargetable target) { //code }
}


public class WeaponController
{
   private List<IWeapon> someWeapons;
   private IWeapon aWeapon;
   private ITargetable currentTarget;

   public void Weapon_OnUse()
   {
       if (!currentTarget.IsHostile) return;

       if (this.IsInMeleeRange(currentTarget))
       {
           aWeapon.Attack();
           return;
       }
       var w = aWeapon as IRangedWeapon;

       if (w != null && w.IsInRange(currentTarget)
       {
           aWeapon.Attack();
           return;
       }

       context.HUD.Warn("Out of range");

   }

   public void Weapon_OnReload()
   {
       var w = aWeapon as IRequiresAmmunition;
       if (w != null) 
       {
            w.Reload();
            context.HUD.DisplayAmmo(w.AmmoRemaining);
       }
   }
}

Answer 3

This seems like what abstract classes and inheritance is for:

public abstract class Weapon {
    public abstract void Attack();
    public abstract void Reload();
}

public class MeleeWeapon : Weapon {
    public override void Attack() {
        // swing sword
    }
    public override void Reload() {
        // ignore reload
    }
}
public class GunWeapon : Weapon {
    public override void Attack() {
        // fire gun
    }
    public override void Reload() {
        // load weapon from inventory
    }
}

public class WeaponController {
    private List<Weapon> someWeapons;
    private Weapon aWeapon;
    public void Main() {
        if (/*"Some action or a button click" */)
            aWeapon.Attack();
        else if (/* some other button click */)
            aWeapon.Reload();
    }
}