Design question - Multiple classes with same functionality

Question

I have some things to clarify for myself, so please bear with me.

Let's say I want to have an object that will explode after a certain period of time. If the object explodes while the person is still holding it, you get killed.

Let's consider the following implementation:

public interface IKillable
{
    void Kill();
}

public interface IExplodable : IKillable
{
     float TimeLeft { get; set; }
     void Timer(float timeToExplode);
}

public abstract class Bomb: IExplodable
{
    public float TimeLeft { get; set; }

    public void Kill()
    {
        //Destroy the object
    }

    public void Timer(float timeLeft)
    {
        if (TimeLeft <= 0) {

            Kill();
        }
    }
}

What if I also want to add let's say a "Backpack" instead of "Bomb" that will have the exact same functionality or any other item that can explode (and kill)?

Is inheriting a "Backpack from Bomb" reasonable in this case?
Probably copying the code won't follow SOLID principles?

I can't understand clearly, the Backpack is exactly same with Bomb? — Seyedraouf Modarresi
– Seyedraouf Modarresi, Commented Jun 23, 2019 at 10:30
Because it can have the same functionality as Bomb (explode). I just gave the bad example.. — rootpanthera
– rootpanthera, Commented Jun 23, 2019 at 10:33
@SeyedRaoufModarresi The question is that a Bomb has the same functionality (explodes and kills) as that of a BackPack, yet the two are different devices — Camilo Terevinto
– Camilo Terevinto, Commented Jun 23, 2019 at 10:41

Camilo Terevinto · Accepted Answer · 2019-06-23 10:54:41Z

1

Having a base class that provides common functionality for objects is both common and recommended in Unity.

Instead of calling the class Bomb, call it something more generic, like ExplodableDevice (as @zmbq answered). I would, however, make it more explicit that the device explods due to a timer, so perhaps TimerExplodableDevice. Notice that the base class should inherit from MonoBehaviour as otherwise you wouldn't be able to use those objects fully (as c# doesn't allow multiple inheritance).

An example of such implementation would be:

public interface IKillable
{
    void Kill();
}

public interface IExplodable : IKillable
{
     float TimeLeft { get; set; }
     void Timer(float timeToExplode);
}

public abstract class TimerExplodableDevice: MonoBehaviour, IExplodable
{
    public float TimeLeft { get; set; }

    public virtual void Kill()
    {
        //Destroy the object
    }

    public virtual void Timer(float timeLeft)
    {
        if (TimeLeft <= 0) 
        {
            Kill();
        }
    }
}

// this should be in a "Devices" folder, or otherwise be called appropriately
public class Backpack : TimerExplodableDevice
{
    void Start()
    {
        TimeLeft = 100;
    }
}

// this should be in a "Devices" folder, or otherwise be called appropriately
public class Bomb : TimerExplodableDevice
{
    void Start()
    {
        TimeLeft = 10;
    }
}

answered Jun 23, 2019 at 10:54

Camilo Terevinto

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2 Comments

rootpanthera Over a year ago

Thanks, this helped! :) Also, why do I need to extend from MonoB in this case?

Camilo Terevinto Over a year ago

@rootpanthera You don't need to, it's only if you want to that you should do it. It depends on the requirements

zmbq · Accepted Answer · 2019-06-23 10:29:19Z

1

You can create an abstract ExplodableDevice class and have Bomb and Backpack inherit from it.

answered Jun 23, 2019 at 10:29

zmbq

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