title: Using a non defined variable in a method
body: <p>Hi im trying to get the Velocity of a transform, this runs in FixedUpdate. Problem is: lastPos stays at null, is there any way to change lastpos to the value of the last cycle without going outside the method? I need this to be scalable.</p>
  <pre><code> void CalculateWing(Vector3? lastPos = null)
      {
          if(lastPos.HasValue == false)
          {
              lastPos = Vector3.zero;
          }
          //This Calculates the Velocity
          Vector3 WingVelocity = (Vector3)((transform.position - lastPos) / Time.fixedDeltaTime);
          //This should save the Position of the last cylcle but is overwritten... 
          lastpos = transform.position
      }
  </code></pre>