write own custom method with out parameter

Question

In Unity I have a gameobject with a trigger attached. This trigger listens to the enter, exit and stay event.

When events get executed the colliding object gets checked for a specific interface component. If this interface component is not null / is attached the code should call a method from the interface component.

Currently I do this

public class LightSource : MonoBehaviour
{
    private void OnTriggerEnter(Collider col)
    {
        HandleLight(col, LightAffectableAction.Enter);
    }

    private void OnTriggerExit(Collider col)
    {
        HandleLight(col, LightAffectableAction.Exit);
    }

    private void OnTriggerStay(Collider col)
    {
        HandleLight(col, LightAffectableAction.Stay);
    }

    private void HandleLight(Collider col, LightAffectableAction action)
    {
        ILightAffectable lightAffectable = col.GetComponent<ILightAffectable>();

        if (lightAffectable != null) // Is the component attached?
        {
            switch (action)
            {
                case LightAffectableAction.Enter:
                    lightAffectable.EnterLight();
                    break;

                case LightAffectableAction.Exit:
                    lightAffectable.ExitLight();
                    break;

                case LightAffectableAction.Stay:
                    lightAffectable.StayInLight();
                    break;
            }
        }
    }

    private enum LightAffectableAction
    {
        Enter,
        Exit,
        Stay
    }
}

but I really don't like using a switch and enum. Maybe a bunch of gameobjects within the trigger will cause performance problems.

Some methods contain a out parameter and I thought about creating something like this

public class LightSource : MonoBehaviour
{
    private void OnTriggerEnter(Collider col)
    {
        if(col.TryGetComponent(ILightAffectable, out ILightAffectable comp)) // Pass in the component type
        {
          comp.EnterLight();
        }
    }

    private void OnTriggerExit(Collider col)
    {
        if(col.TryGetComponent(ILightAffectable, out ILightAffectable comp))
        {
          comp.ExitLight();
        }
    }

    private void OnTriggerStay(Collider col)
    {
        if(col.TryGetComponent(ILightAffectable, out ILightAffectable comp))
        {
          comp.StayInLight();
        }
    }
}

but I don't know how to create an extension method like TryGetComponent that fits to the example code above.

I pass in a component type as parameter and get the component as a out parameter.

How can I create such a method?

Lennart Stoop · Accepted Answer · 2018-09-24 09:34:50Z

1

You could create a generic extension method just like the existing GetComponent method.

public static class ColliderExtensions
{
  public static bool TryGetComponent<T>(this Collider collider, out T component) where T : class
  {
    component = collider.GetComponent<T>();
    return component != null;
  }
}

Usage:

ILightAffectable component;
if (col.TryGetComponent(out component))
{
  component.ExitLight();
}

answered Sep 24, 2018 at 9:34

Lennart Stoop

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