title: Child calling a parent function that uses child's function in Unity
body: <p>I have a base class that has a function that does not know what one of the functions it calls will do. That behavior is defined in the child. The parents function is then called from the child. What is the correct syntax/method to make this work? Particularly what must I put instead of <code>FunctionToBeDefinedLater</code> Example follows:</p>
  
  <pre><code>public class ToolScript : MonoBehaviour {
      public void isActive()
      {
          if (Input.GetKeyDown("space"))
          {
              Use();
          }
      }
      FunctionToBeDefinedLater Use();
  }
  
  public class GunController : ToolScript
  {
      public void Use()
      {
        //Spawn bullet at this direction, this speed, give it spiral, tons of behavior etc. etc.
      }
      private void Update()
      {
        isActive();
      }
  }
  
  public class FlamethrowerController : ToolScript
  {
      public void Use()
      {
        //Spawn fire at this direction, this speed, set tip of flamethrower to be red etc etc
      }
      private void Update()
      {
        isActive();
      }
  
  }
  </code></pre>
  
  <p>The <code>Update</code> function is from unity and is called every frame. Please let me know if I can clarify my question any further and I will do so as soon as possible. I do not know if this is referencing overriding, interfacing, or abstraction so I have tagged them all. I will fix this as soon as I know.</p>