Inheritance Issue

So I'm having an issue based on the design discussed here.

I'll reiterate them here.

I have 2 hierarchies of classes as follows:

ActionManager : Monobehavior
PlayerActionManager : ActionManager
EnemyActionManager : ActionManager

and

StatsManager : MonoBehavior
PlayerStats : StatManager
EnemyStats : StatManager

My ActionManager class (which is abstract) has a stats object of type StatManager. Herein lies the problem.

In PlayerActionManager, I want it to be an instance of PlayerStats, and in EnemyActionManager, I want it to be an instance of EnemyStats.

My first question is: Is there a way to tell a derived class that an object inherited from its base class should actually be a sub-type of the object it inherited. For example, can I tell PlayerActionManager that its stats object (type StatManager in ActionManager) must be of type PlayerStats?

To be clear on what I'm trying to do:

StatManager has variables and objects common to both PlayerStats and EnemyStats, but each of the child classes add new variables. One of those new variables in PlayerStats is wpnDam.

As I've said, stats is of type StatManager, which doesn't have a wpnDam variable, so I'm unable to access wpnDam from inside PlayerActionManager.

Code (CSharp):

1. stats.dam = Randomizer.randomize(stats.wpnDam / stats.wpnDamMod, stats.wpnDam) + stats.str + Randomizer.randomize(stats.str / stats.strMod, stats.str);

I get a hint that there is no definition for wpnDam in StatsManager (which, of course, is true).

I would just define stats in each sub-class, but I have a method TakeDamage in ActionManager which needs access to it, because both the player and enemies take damage in the same way.

I appreciate any help.

Thanks.

 

Why not just have two variables, one of type PlayerStats and the other of type EnemyStats?

The other alternative is to cast. Something like this

Code (CSharp):

1. EnemyStats enemyStats = (EnemyStats)statsManager;

 

Thanks, I think I might be able to make that work.

 

This looks like something I would like to use, but I would like to understand it a little better before doing so.

What exactly does declaring PlayerActionManager as follows do?

Code (CSharp):

1. class PlayerActionManager : ActionManager<PlayerStats>{
2. ...
3. }

Does that mean I'm replacing every occurrence of the symbol T in the class with whatever I plug in in the subclass (in this case, PlayerStats)?

If so, does this mean I can specify multiple generic types using something like

Code (CSharp):

1. ActionManager<T, U> : MonoBehaviour

And specify multiple types in subclasses just by replacing T and U with the types I want to use?

Also, how would I rewrite my TakeDamage method to use the generic type? Or would I even have to?

Code (CSharp):

1. public void TakeDamage(float damageIn){
2.         stats.def = stats.armorDef + Randomizer.randomize(stats.con / stats.conMod, stats.con);
3.        
4.         float totalDamage = damageIn - stats.def;
5.         totalDamage = (totalDamage >= 1) ? totalDamage : 1;
6.        
7.         Debug.Log ("takeDamage: def is " + stats.def + " damageIn is " + damageIn + " totalDamage is " + totalDamage);
8.         stats.hp -= totalDamage;
9.         if (stats.hp <= 0) {
10.             GetComponentInChildren<Animator>().SetTrigger("Die");
11.             Destroy(gameObject.rigidbody, 0);
12.             Destroy(gameObject.collider);
13.         }
14.         Debug.Log("takeDamage: health is " + stats.hp);
15.     }

 

I've changed the code to use T instead of StatManager, and now PlayerActionManager and EnemyActionManager are happy, but....

Without changing the code, the code analyzer doesn't like me trying to access any members in StatManager using stats.someMember. It says that T has no member someMember. Also, Unity won't compile it.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public abstract class ActionManager<T> : MonoBehaviour {
5.  
6.     public T stats; //used to be public StatManager stats
7.  
8.     public abstract void Attack();
9.  
10.     public abstract void Die();
11.  
12.     public void TakeDamage(float damageIn){
13.         stats.def = stats.armorDef + Randomizer.randomize(stats.con / stats.conMod, stats.con);
14.      
15.         float totalDamage = damageIn - stats.def;
16.         totalDamage = (totalDamage >= 1) ? totalDamage : 1;
17.      
18.         Debug.Log ("takeDamage: def is " + stats.def + " damageIn is " + damageIn + " totalDamage is " + totalDamage);
19.         stats.hp -= totalDamage;
20.         if (stats.hp <= 0) {
21.             GetComponentInChildren<Animator>().SetTrigger("Die");
22.             Destroy(gameObject.rigidbody, 0);
23.             Destroy(gameObject.collider);
24.         }
25.         Debug.Log("takeDamage: health is " + stats.hp);
26.     }
27. }

How can I solve this?

P.S. Note that TakeDamage is defined in ActionManager

 

constrain T

Code (csharp):

1.  
2. public abstract class ActionManager<T> : MonoBehaviour where T : StatsManager
3.  

 

Beautiful. I think this is exactly what I was trying to do.

By putting on this constraint, am I also constraining subclasses to use only StatManager or its subtypes in place of T?

 

Wow, this is going to be super useful, and would have taken me forever to find out on my own.

Thanks guys. This community is great.