Item/Ability system using scriptableobjects in Unity

Question

I'm new to Unity and I'm having some trouble creating scriptable objects for items to pick up and use in my project. I've created the initial set-up to make the items with variables that I can plug-and-play with.

What I'm trying to do is:

1 - plug in a monobehavior script for each new item's behavior when used.

2 - Allow the player to pick up the item on collision and use the item on key command. The player should only carry one item at a time.

Here is what I have so far.

the scriptable object (itemObject.cs)

[CreateAssetMenu(fileName = "New Item", menuName = "Item")]
public abstract class Item : ScriptableObject {
                public new string name;
                public string description;
                public int damageAmount;
                public int affectDelay;
                public int affectDuration;
                public int affectRange;
                public float dropChance;
                public float itemLife;
}

I have a script that will trigger if the player collides with the object (itemDisplay.cs) Currently, this doesn't do anything but destroys the item.

public class itemDisplay : MonoBehaviour {

public Item item;

public static bool isActive = false;

void OnTriggerEnter(Collider other)
{

    if (other.gameObject.tag == "Player")
    {

        var playerPickUp = other.gameObject;

        var playerScript = playerPickUp.GetComponent<Player>();
        var playerItem = playerScript.playerItem;

        playerScript.pickUpItem();

        bool isActive = true;

        Object.Destroy(gameObject);

    }
}


void Start () {

}


void Update(){
}

}

Currently, I have a pickup function and a use item function that's being handled by my player script(Player.cs). Currently, this just toggles a boolean saying that it did something when the item is collided with. My big question is how/where should I create and reference the item ability and how do I pass it to the player script here?

public void pickUpItem()
{
    playerItem = true;
    //itemInHand = itemInHand;
    Debug.Log("You Picked Up An Item!");

   // Debug.Log(playerItem);
    if(playerItem == true){
        Debug.Log("This is an item in your hands!");
    }

}

public void useItem()
{
    //use item and set
    //playerItem to false
    playerItem = false;


}

Answer 1

If your question is "how do I create an instance of an Item in my project", you do that by right clicking in your Project view, then selecting Create -> Item. Then drag the Item asset that you created from your Project view into the ItemDisplay scene object's item field in the Inspector.

Regarding how to pick up the item, you would pass the item to your Player script from your ItemDisplay script. You've got most of that already wired up.

public class ItemDisplay : MonoBehaviour
{
   void OnTriggerEnter(Collider other)
   {
      if (other.gameObject.tag == "Player")
      {
         var playerPickUp = other.gameObject;

         var playerScript = playerPickUp.GetComponent<Player>();
         var playerItem = playerScript.playerItem;

         // This is where you would pass the item to the Player script
         playerScript.pickUpItem(this.item);

         bool isActive = true;

         Object.Destroy(gameObject);
      }
   }
}

Then in your Player script...

public class Player : MonoBehaviour
{
   public void PickUpItem(Item item)
   {
      this.playerItem = true;
      this.itemInHand = item;
      Debug.Log(string.Format("You picked up a {0}.", item.name));
   }

   public void UseItem()
   {
      if (this.itemInHand != null)
      {
         Debug.Log(string.Format("You used a {0}.", this.itemInHand.name));
      }
   }
}

You should also make your Item class non-abstract, or leave it abstract and create the appropriate non-abstract derived classes (Weapon, Potion, etc.). I put an example of that below.

You can't attach a MonoBehaviour to a ScriptableObject if that's what you're trying to do. A ScriptableObject is basically just a data/method container that isn't tied to a scene. A MonoBehaviour has to live on an object within a scene. What you could do however, is add a "use" method to your Item class, and call that from a MonoBehaviour within the scene when the player uses an item.

public abstract class Item : ScriptableObject
{
   // Properties that are common for all types of items
   public int weight;
   public Sprite sprite;

   public virtual void UseItem(Player player)
   {
      throw new NotImplementedException();
   }
}


[CreateAssetMenu(menuName = "Items/Create Potion")]
public class Potion : Item
{
   public int healingPower;
   public int manaPower;

   public override void UseItem(Player player)
   {
      Debug.Log(string.Format("You drank a {0}.", this.name));

      player.health += this.healingPower;          
      player.mana += this.manaPower;
   }
}

[CreateAssetMenu(menuName = "Items/Create Summon Orb")]
public class SummonOrb : Item
{
   public GameObject summonedCreaturePrefab;

   public override void UseItem(Player player)
   {
      Debug.Log(string.Format("You summoned a {0}", this.summonedCreaturePrefab.name));

      Instantiate(this.summonedCreaturePrefab);
   }
}

Then change your UseItem method in Player:

public class Player : MonoBehaviour
{
   public void UseItem()
   {
      if (this.itemInHand != null)
      {
         this.itemInHand.UseItem(this);
      }
   }
}