movingobject

using UnityEngine;
using System.Collections;


    //The abstract keyword enables you to create classes and class members that are incomplete and must be implemented in a derived class.
    public abstract class MovingObject : MonoBehaviour
    {
        public float moveTime = 0.01f;           //Time it will take object to move, in seconds.
        public LayerMask blockingLayer;         //Layer on which collision will be checked.


        private BoxCollider2D boxCollider;      //The BoxCollider2D component attached to this object.
        private Rigidbody2D rb2D;               //The Rigidbody2D component attached to this object.
        private float inverseMoveTime;          //Used to make movement more efficient.


        //Protected, virtual functions can be overridden by inheriting classes.
        protected virtual void Start ()
        {
            //Get a component reference to this object's BoxCollider2D
            boxCollider = GetComponent <BoxCollider2D> ();

            //Get a component reference to this object's Rigidbody2D
            rb2D = GetComponent <Rigidbody2D> ();

            //By storing the reciprocal of the move time we can use it by multiplying instead of dividing, this is more efficient.
            inverseMoveTime = 1f / moveTime;
        }


        //Move returns true if it is able to move and false if not.
        //Move takes parameters for x direction, y direction and a RaycastHit2D to check collision.
        protected bool Move (int xDir, int yDir, out RaycastHit2D hit)
        {
            //Store start position to move from, based on objects current transform position.
            Vector2 start = transform.position;

            // Calculate end position based on the direction parameters passed in when calling Move.
            Vector2 end = start + new Vector2 (xDir, yDir);

            //Disable the boxCollider so that linecast doesn't hit this object's own collider.
            boxCollider.enabled = false;

            //Cast a line from start point to end point checking collision on blockingLayer.
            hit = Physics2D.Linecast (start, end, blockingLayer);

            //Re-enable boxCollider after linecast
            boxCollider.enabled = true;

            //Check if anything was hit
            if(hit.transform == null)
            {
                //If nothing was hit, start SmoothMovement co-routine passing in the Vector2 end as destination
                StartCoroutine (SmoothMovement (end));

                //Return true to say that Move was successful
                return true;
            }

            //If something was hit, return false, Move was unsuccesful.
            return false;
        }


        //Co-routine for moving units from one space to next, takes a parameter end to specify where to move to.
        protected IEnumerator SmoothMovement (Vector3 end)
        {
            //Calculate the remaining distance to move based on the square magnitude of the difference between current position and end parameter.
            //Square magnitude is used instead of magnitude because it's computationally cheaper.
            float sqrRemainingDistance = (transform.position - end).sqrMagnitude;

            //While that distance is greater than a very small amount (Epsilon, almost zero):
            while(sqrRemainingDistance > float.Epsilon)
            {
                //Find a new position proportionally closer to the end, based on the moveTime
                Vector3 newPostion = Vector3.MoveTowards(rb2D.position, end, inverseMoveTime * Time.deltaTime);

                //Call MovePosition on attached Rigidbody2D and move it to the calculated position.
                rb2D.MovePosition (newPostion);

                //Recalculate the remaining distance after moving.
                sqrRemainingDistance = (transform.position - end).sqrMagnitude;

                //Return and loop until sqrRemainingDistance is close enough to zero to end the function
                yield return null;
            }
        }


        //The virtual keyword means AttemptMove can be overridden by inheriting classes using the override keyword.
        //AttemptMove takes a generic parameter T to specify the type of component we expect our unit to interact with if blocked (Player for Enemies, Wall for Player).
        protected virtual void AttemptMove <T> (int xDir, int yDir)
            where T : Component
        {
            //Hit will store whatever our linecast hits when Move is called.
            RaycastHit2D hit;

            //Set canMove to true if Move was successful, false if failed.
            bool canMove = Move (xDir, yDir, out hit);

            //Check if nothing was hit by linecast
            if(hit.transform == null)
                //If nothing was hit, return and don't execute further code.
                return;

            //Get a component reference to the component of type T attached to the object that was hit
            T hitComponent = hit.transform.GetComponent <T> ();

            //If canMove is false and hitComponent is not equal to null, meaning MovingObject is blocked and has hit something it can interact with.
            if(!canMove && hitComponent != null)

                //Call the OnCantMove function and pass it hitComponent as a parameter.
                OnCantMove (hitComponent);
        }


        //The abstract modifier indicates that the thing being modified has a missing or incomplete implementation.
        //OnCantMove will be overriden by functions in the inheriting classes.
        protected abstract void OnCantMove <T> (T component)
            where T : Component;
    }