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How to correctly use abstract and virtual methods?

I am trying to use virtual and abstract methods to make my game architecture better.
I'm using C# and Unity for this example.
I use a ShipComponent as a base Class because I want all the child classes to do the same thing.
But sometimes I want a certain ShipComponent to do something else.
The code will make it a lot clearer:
ShipComponent.cs:
public abstract class ShipComponent : MonoBehaviour
{
[HideInInspector] public ShipControl shipControl;
public virtual void Init(ShipControl control)
{
this.shipControl = control;
}
public virtual void IsPlayer()
{
SetListeners();
}
public abstract void IsNotPlayer();
public abstract void ReEnable();
public abstract void SetListeners();
}
One of the many child classes that inherits from ShipComponent:
public class Rudder : ShipComponent
{
[Header("Settings")]
public Transform rudder;
[Header("Debug Info")]
[SerializeField] float rudderSpeed;
[SerializeField][Range(-45, 45)] int setRudderAngle = 0;
[SerializeField][Range(-45f, 45f)] float realRudderAngle = 0f;
public override void Init(ShipControl shipControl)
{
base.Init(shipControl);
rudder = transform.GetChild(0).GetChild(4);
StartCoroutine(SmoothRudderChange());
SetListeners();
}
public override void IsPlayer()
{
base.IsPlayer();
}
public override void IsNotPlayer()
{
PlayerShipControl.OnRudderChange -= SetRudder;
}
public override void ReEnable()
{
StartCoroutine(SmoothRudderChange());
SetListeners();
}
public override void SetListeners()
{
PlayerShipControl.OnRudderChange -= SetRudder;
if (!shipControl.shipWrapper.ship.IsPlayer) return;
PlayerShipControl.OnRudderChange += SetRudder;
}
void OnDisable()
{
PlayerShipControl.OnRudderChange -= SetRudder;
StopAllCoroutines();
}
The main draw back I experience with this, is that I have to copy paste all 5 or 6 methods everytime I create a new ShipComponent class.
It seems messy and theres a lot of repeating code, most of the time the only difference in each ShipComponent is the SetListeners part, and StartCoroutines if any.
Is there a way to dynamically set delegate listeners up?
So I could set them in the base class ShipComponent?
Instead of setting each component individually?
Another script that inherits from ShipComponent for completeness:
public class Guns : ShipComponent
{
IEnumerator mouseAimCycle;
public override void Init(ShipControl shipControl)
{
base.Init(shipControl);
InitCannons();
SetListeners();
}
public override void ReEnable()
{
SetListeners();
}
public override void IsPlayer()
{
base.IsPlayer();
mouseAimCycle = AimCycle();
StartCoroutine(mouseAimCycle);
SetListeners();
}
public override void SetListeners()
{
PlayerShipControl.OnFireGuns -= TryFire;
if (!shipControl.shipWrapper.ship.IsPlayer) return;
PlayerShipControl.OnFireGuns += TryFire;
}
public override void IsNotPlayer()
{
StopCoroutine(mouseAimCycle);
PlayerShipControl.OnFireGuns -= TryFire;
}
void OnDisable()
{
PlayerShipControl.OnFireGuns -= TryFire;
StopAllCoroutines();
}
Calling the ShipComponent virtual and abstract methods:
public class ShipControl : MonoBehaviour
{
// Contains Ship + Cargo + Crew and a ref to this ShipControl
public ShipWrapper shipWrapper { get; private set; }
ShipComponent[] shipComponents;
// Gather all ShipComponents and Initialize them.
public void Start()
{
shipComponents = transform.GetComponents<ShipComponent>();
foreach (ShipComponent comp in shipComponents)
{
comp.Init(this);
}
}
// Call this to check if this is players current ship and set the components accordingly.
public void UpdateIsPlayer()
{
if (!shipWrapper.ship.IsPlayer)
foreach (ShipComponent component in shipComponents)
component.IsNotPlayer();
else
foreach (ShipComponent component in shipComponents)
component.IsPlayer();
}
And PlayerShipControl, which I use for input, broadcasting the input through delegates, and the theory is that only the players currently controlled ship will be listening for this input:
public class PlayerShipControl : MonoBehaviour
{
public static event Action<Transform> SetCamToPlayerShip;
public static event Action SetShipPanelUI;
public static event Action<bool> ToggleAnchorIcon, ToggleFlagIcon, ToggleAutofireIcon, ToggleBoatsIcon;
public static event Action OnFireGuns;
public static event Action<int> OnRudderChange;
public static event Action<int> OnSailStateChange;
public static event Action<bool> OnAllAnchorsCommand;
public static event Action<bool> OnAllBoatsCommand;
bool anchor, flag, autofire, boats;
ShipControl shipControl;
void Update()
{
if (Input.GetKeyUp(KeyCode.W)) // Raise Sails SailState++
{
OnSailStateChange?.Invoke(1);
}
if (Input.GetKeyUp(KeyCode.S)) // Furl Sails SailState--
{
OnSailStateChange?.Invoke(-1);
}
if (Input.GetKey(KeyCode.D))
{
OnRudderChange?.Invoke(1);
}
if (Input.GetKey(KeyCode.A))
{
OnRudderChange?.Invoke(-1);
}
if (Input.GetKeyDown(KeyCode.M))
{
OnRudderChange?.Invoke(0);
}
// Drop All Anchors
if (Input.GetKeyDown(KeyCode.V))
{
anchor = true;
ToggleAnchorIcon?.Invoke(anchor);
OnAllAnchorsCommand?.Invoke(anchor);
}
// Haul All Anchors
if (Input.GetKeyDown(KeyCode.H))
{
anchor = false;
ToggleAnchorIcon?.Invoke(anchor);
OnAllAnchorsCommand?.Invoke(anchor);
}
// Drop All Boats
if (Input.GetKeyDown(KeyCode.B))
{
boats = true;
ToggleBoatsIcon?.Invoke(boats);
OnAllBoatsCommand?.Invoke(boats);
}
// Take In All Boats
if (Input.GetKeyDown(KeyCode.U))
{
OnAllBoatsCommand?.Invoke(false);
// TO DO When all boats are back on deck, boatIcon + boatsBoolFlag should be turned off again.
}
if (Input.GetKeyDown(KeyCode.Space))
{
OnFireGuns?.Invoke();
}
}
}
Its a long string of scripts sometimes though so I have left out all the managers and such.
Ship ship inside shipWrapper.ship is a custom data class that stores the info about the ship, not a Monobehaviour, but it holds a bool called IsPlayer aswell. Nothing else of interest I can think of.

The main draw back I experience with this, is that I have to copy paste all 5 or 6 methods every time I create a new ShipComponent class. It seems messy and there's a lot of repeating code, most of the time the only difference in each ShipComponent is the SetListeners part, and StartCoroutines if any.
In the show example you have more differences between implementations then ones described. Without seeing the full code it is hard to suggest something meaningful.
Few notes on the current code:
In Rudder you don't need to specify IsPlayer because the following:
public override void IsPlayer()
{
base.IsPlayer();
}
does not add anything extra, so you can just skip implementation in the derived class.
Based on provided examples it seems that ReEnable can be defined as virtual in base class with default implementation set to calling SetListeners (the same approach as you have with Init and IsPlayer).
PlayerShipControl.Update possibly can be improved by moving handlers to dictionary. Something along this lines:
public class PlayerShipControl : MonoBehaviour
{
// ...
Dictionary<KeyCode, Action> keyActions = new() // not sure about the type
{
{ KeyCode.W, () => OnSailStateChange?.Invoke(1) },
// ...
{ KeyCode.V, () =>
{
anchor = true;
ToggleAnchorIcon?.Invoke(anchor);
OnAllAnchorsCommand?.Invoke(anchor);
}
},
// ...
};
void Update()
{
foreach (var kvp in keyActions)
{
if (Input.GetKeyUp(kvp.Key))
{
kvp.Value();
break;
}
}
}
}

Implementing multiple behaviors on a child class from a method on a root class

I'm looking to implement a certain behavior but I'm not sure how to implement it.
Given a base class :
public class Base
{
void Start() { }
void Update() { }
}
And these two classes which inherit it.
public class Behavior1 : Base
{
private int member;
void Start() { member = 0; }
void Update() { member++; }
}
public class Behavior2 : Base
{
private string name;
void Start() { name = "some string"; }
void Update() { if(name) { Console.WriteLine(name) } }
}
And then a final class which I wish to inherit the logic of the two sub classes.
public class Child : Base // ? Behavior1, Behavior2
{
void Start() { } // logic and members implemented but don't need to be referenced
void Update() { }
}
How would I go about having the Child class implement the two Behavior classes? I don't think you can inherit more than one class at a time so I can't do that. Is there another construct which can accomplish this?

Wihtout enter to valorate the inheritance, that probably need some think as you can read in the comments, you can do something like this if you want use both behaviors ni a class that doesn't inherith them:
public class Child : Base
{
private readonly Behavior1 _behavior1;
private readonly Behavior2 _behavior2;
public Child()
{
this._behavior1 = new Behavior1();
this._behavior2 = new Behavior2();
}
public override void Start()
{
this._behavior1.Start();
}
public override void Update()
{
this._behavior2.Update();
}
}
You can also inherith from Behavior1 and only add Behavior2 as a field:
public class Child : Behavior1
{
private readonly Behavior2 _behavior2;
public Child()
{
this._behavior2 = new Behavior2();
}
public override void Update()
{
this._behavior2.Update();
}
}
But, as I said, is probably that you find a better solution thinking about your models and their composition/inheritance.

Inheritance, need advices

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...

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);
}
}
}

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();
}
}

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.

Inheritance chain in state machine branching out

I am trying to do a state machine to controll ai behaviour in Unity 3D.
My question is regarding inheritance. Im trying to set up some base logic that handles how and why states shoul be changed. But further down the inheritance line i need different kind of characters to be able to do character speicfic things. But im not able to do this with inheritnance.
Can someone confirm that my thinking is not how its done? then i know to find another solution.
PSEUDO CODE:
// STATE CONTROLLERS CONTROLL THE CHARACETER BY CHOOSING WITCH STATE THEY SHOULD BE IN
abstract class StateController {
StateBase state;
int HitPoints;
int Hunger:
abstract void Update()
{
CheckIfStateShouldChange();
state.UpdateState(this);
}
}
WolfStateController : StateController {
WolfState state;
override void Update()
{
base.Update();
state.Update(this);
}
}
SheepStateController : StateController {
SheepState state;
override void Update()
{
base.Update();
state.Update(this);
}
}
// STATES CONTAINS LOGIC FOR BEHAVIOUR IN A CERTAIN STATE
StateBase {
virtual void UpdateState( StateController controller)
{
// Does things all inheriting classes should do
}
}
WolfState : StateBase {
override void UpdateState( WolfStateController wolfstate)
{
base.UpdateState(WolfStateController wolfstate)
//Does wolf specific things that needs to be done in all WolfStates
}
}
WolfStalkAndHuntState : WolfState {
override void UpdateState( WolfStateController wolfstate)
{
base.UpdateState(WolfStateController wolfState);
//Hunts sheep and attacks on sight
}
}
SheepState : StateBase {
override void UpdateState( SheepStateController sheepState)
{
//Does sheepy things
}
}
SheepReproduceState : SheepState {
override void UpdateState( SheepStateController sheepState)
{
base.UpdateState(SheepStateController sheepState);
// Looks for mate and gets freaky
}
}

I would suggest something like this:
Controller Class:
public class SoliderController : MonoBehaviour
{
[HideInInspector] public sState currentState;
[HideInInspector] public FireState fireState;
[HideInInspector] public IdleState idleState;
[HideInInspector] public ChaseState chaseState;
private void Awake()
{
fireState = new FireState(this);
idleState = new IdleState(this);
chaseState = new ChaseState(this);
}
private void Start ()
{
currentState = idleState;
}
private void Update()
{
currentState.Update();
}
Interface:
public abstract class sState
{
public abstract void Update();
public abstract void ToChaseState();
public abstract void ToIdleState();
public abstract void ToFireState();
}
Example Class
public class IdleState : sState
{
private readonly SoliderController controller;
public IdleState(SoliderController soliderController)
{
controller = soliderController;
}
public override void Update()
{
Patrol();
//Condition to change state
if (*expresion1*)
ToChaseState();
if (*expresion2*)
ToFireState();
}
private void Patrol()
{
//Your Logic for the behvaiour wanted.
}
public override void ToChaseState()
{
controller.currentState = controller.chaseState;
}
public override void ToFireState()
{
controller.currentState = controller.fireState;
}
public override void ToIdleState()
{
Debug.LogWarning("Can't transition to same state");
}
}
This way checking for changes is way easier and also you can impletement state specific behaviours as well. Also, adding a new state goes really easy, you just implement the new Class and ToNewState method in the interface.
Hope it helped.

C# Is interface casting a violation of the Liskov Substitution Principle

I would like to refer to the example that was used before on SO
with the Duck and Electric Duck:
public interface IDuck
{
void Swim();
}
public class Duck : IDuck
{
public void Swim()
{
//do something to swim
}
}
public class ElectricDuck : IDuck
{
public void Swim()
{
if (!IsTurnedOn)
return;
//swim logic
}
public void TurnOn()
{
this.IsTurnedOn = true;
}
public bool IsTurnedOn { get; set; }
}
The original violation for LSP would look like this:
void MakeDuckSwim(IDuck duck)
{
if (duck is ElectricDuck)
((ElectricDuck)duck).TurnOn();
duck.Swim();
}
One solution by the author was to put the Logic inside the electric duck's swim method to turn itself on:
public class ElectricDuck : IDuck
{
public void Swim()
{
if (!IsTurnedOn)
TurnOn();
//swim logic
}
public void TurnOn()
{
this.IsTurnedOn = true;
}
public bool IsTurnedOn { get; set; }
}
I have come across other scenarios where an extended interface can be created that supports some sort of initialization:
public interface IInitializeRequired
{
public void Init();
}
Electric Duck could then be extended with this interface:
public class ElectricDuck : IDuck, IInitializeRequired
{
public void Swim()
{
if (!IsTurnedOn)
return;
//swim logic
}
public void TurnOn()
{
this.IsTurnedOn = true;
}
public bool IsTurnedOn { get; set; }
#region IInitializeRequired Members
public void Init()
{
TurnOn();
}
#endregion
}
EDIT: The reason for the extended interface Is based on the author saying that turning on automatically in the swim method might have other undesired results.
Then the method instead of checking and casting to a specific type can look for an extended interface instead:
void MakeDuckSwim2(IDuck duck)
{
var init = duck as IInitializeRequired;
if (init != null)
{
init.Init();
}
duck.Swim();
}
The fact that i made the initialization concept more abstract then to create an extended interface called IElectricDuck with TurnOn() method, may make this seem that I did the right thing, however the whole Init concept may only exist because of electric duck.
Is this a better way/solution or is this just an LSP violation in disguise.
Thanks

It's an LSP violation in disguise. Your method accepts an IDuck, but it requries verification of the dynamic type (whether the IDuck implements IInitializeRequired or not) to work.
One possibility to fix this would be to accept the fact that some ducks require initialization and redefine the interface:
public interface IDuck
{
void Init();
/// <summary>
/// Swims, if the duck has been initialized or does not require initialization.
/// </summary>
void Swim();
}
Another option is to accept that an uninitialized ElectricDuck is not really a duck; thus, it does not implement IDuck:
public class ElectricDuck
{
public void TurnOn()
{
this.IsTurnedOn = true;
}
public bool IsTurnedOn { get; set; }
public IDuck GetIDuck()
{
if (!IsTurnedOn)
throw new InvalidOperationException();
return new InitializedElectricDuck(); // pass arguments to constructor if required
}
private class InitializedElectricDuck : IDuck
{
public void Swim()
{
// swim logic
}
}
}

I would still consider your final example as an LSP violation because logically you do exactly this. As you said, there is no concept of initialization really, it is just made up as a hack.
Indeed, your MakeDuckSwim method should not know anything about any duck's specifics (whether it should be initialized first, fed with some destination after initialization, etc).
It just has to make the provided duck swim!
It is hard to tell on this example (as it is not real), but looks like somewhere "upper" there is a factory or something that creates you a specific duck.
It it possible that you miss the concept of a factory here?
If there was one, then It should know what duck it is creating exactly so probably it should be responsible to know how to initialize a duck, and the rest of your code just works with IDuck without any "ifs" inside behavioral methods.
Obviously you can introduce the concept of "initialization" straight to IDuck interface. Say, a "normal" duck needs to be fed, an electrical one needs to be turned on, etc :) But it sounds a bit dodgy :)

I think first you need to answer this question about electric ducks - do they turn themselves on automatically when someone asks them to swim? If so, turn them on in the Swim method.
If not, it is the duck's client responsibility for turning it on, and you might as well just throw an InvalidOperationException if the duck can't swim because it's turned off.

public interface ISwimBehavior
{
void Swim();
}
public interface IDuck
{
void ISwimBehavior { get; set; }
}
public class Duck : IDuck
{
ISwimBehavior SwimBehavior { get { return new SwimBehavior(); }; set; }
}
public class ElectricDuck : IDuck
{
ISwimBehavior SwimBehavior { get { return new EletricSwimBehavior(); }; set; }
}
The behaviour classes:
public class SwimBehavior: ISwimBehavior
{
public void Swim()
{
//do something to swim
}
}
public class EletricSwimBehavior: ISwimBehavior
{
public void Swim()
{
if (!IsTurnedOn)
this.TurnOn();
//do something to swim
}
public void TurnOn()
{
this.IsTurnedOn = true;
}
public bool IsTurnedOn { get; set; }
}

Maybe something like this:
public interface IDuck
{
bool CanSwim { get; }
void Swim();
}
public class Duck : IDuck
{
public void Swim()
{
//do something to swim
}
public bool CanSwim { get { return true; } }
}
public class ElectricDuck : IDuck
{
public void Swim()
{
//swim logic
}
public void TurnOn()
{
this.IsTurnedOn = true;
}
public bool IsTurnedOn { get; set; }
public bool CanSwim { get { return IsTurnedOn; } }
}
Client would be changed like:
void MakeDuckSwim(IDuck duck)
{
if (duck.CanSwim)
{
duck.Swim();
}
}