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Shimizoki

•Created by Shimizoki on 2/8/2023 in #help

❔ [Unity?] How to have a list of generic classes in inspector cast as derived class

I have some classes as follows:

c#
[System.Serializable]
public class TrackedMarkers<T, U>
  where T : MarkerScriptable
  where U : MarkerInterface 
{
  string tag;
  public T t;
  public U u;
}

public abstract class MarkerInterface : MonoBehaviour {
  public virtual void myFunc() {}
}

public class Marker1 : MarkerInterface {
  public int color;
  public override void myFunc() {}
 }  
public class Marker2 : MarkerInterface {
  public int count;
  public override void myFunc() {}
 }  

public class MarkerScriptable : ScriptableObject {
  public int[] ids = new int[0];
}

 public class Scriptable1 : MarkerScriptable { /* unique stuff */ }
 public class Scriptable2 : MarkerScriptable { /* unique stuff */ }

c#
[System.Serializable]
public class TrackedMarkers<T, U>
  where T : MarkerScriptable
  where U : MarkerInterface 
{
  string tag;
  public T t;
  public U u;
}

public abstract class MarkerInterface : MonoBehaviour {
  public virtual void myFunc() {}
}

public class Marker1 : MarkerInterface {
  public int color;
  public override void myFunc() {}
 }  
public class Marker2 : MarkerInterface {
  public int count;
  public override void myFunc() {}
 }  

public class MarkerScriptable : ScriptableObject {
  public int[] ids = new int[0];
}

 public class Scriptable1 : MarkerScriptable { /* unique stuff */ }
 public class Scriptable2 : MarkerScriptable { /* unique stuff */ }

In my main script I am attempting to have a list of Tracked Markers in the inspector, But if I initialize my list as  

c#
  public List<TrackedMarkers<MarkerScriptable, MarkerInterface>> myList;

  // In inspector I slot
  // myList[0] = (Marker1, Scriptable1)
  // myList[1] = (Marker2, Scriptable2)

c#
  public List<TrackedMarkers<MarkerScriptable, MarkerInterface>> myList;

  // In inspector I slot
  // myList[0] = (Marker1, Scriptable1)
  // myList[1] = (Marker2, Scriptable2)

  Then when I try and cast it later, I get the expected 

c#
string t = myList[0].tag;
// Above line works
var tm = myList[0] as TrackedMarker<Scriptable1, Marker1>; 
// error CS0039: Cannot convert type 'TrackedMarkers<MarkerScriptable, MarkerInterface>' to 'TrackedMarkers<Scriptable1, Marker1>' via a reference conversion, boxing conversion, unboxing conversion, wrapping conversion, or null type conversion

c#
string t = myList[0].tag;
// Above line works
var tm = myList[0] as TrackedMarker<Scriptable1, Marker1>; 
// error CS0039: Cannot convert type 'TrackedMarkers<MarkerScriptable, MarkerInterface>' to 'TrackedMarkers<Scriptable1, Marker1>' via a reference conversion, boxing conversion, unboxing conversion, wrapping conversion, or null type conversion

   I somewhat understand why… If it was stored in the baseClass list, it would not know which child it belongs to. However in unity the objects that I am slotting in are already the derived class… so it should be available.

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