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  • Subject area(s): Science
  • Price: Free download
  • Published on: 15th October 2019
  • File format: Text
  • Number of pages: 2

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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 = 0.4f; //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)

{

float scale = (float)Utilities.SCALE_REF / (float)Utilities.MAZE_SIZE;

//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*scale, yDir*scale);

//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;

}

GameManager.instance.boardScript.set_left_start_pt (true);

}

//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 bool 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);

if (canMove) {

OnMove();

}

//Check if nothing was hit by linecast

if (hit.transform == null)

//If nothing was hit, return and don't execute further code.

return true;

//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);

return canMove;

}

//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;

protected abstract void OnMove();

}

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