Iterator Pattern in Unity

Overview

This project demonstrates the use of the Iterator Pattern in Unity by implementing a patrol system for an NPC (Non-Player Character). The NPC moves between predefined patrol points in the scene, showcasing the principles of the Iterator Pattern to navigate through a collection of points.

Features

• NPC Movement: The NPC patrols between multiple points in the scene.
• Iterator Pattern: Uses the Iterator design pattern to navigate the patrol points.
• Modular Design: The code adheres to SOLID principles, ensuring maintainability and clarity.

Components

1. PatrolRoute.cs

This class manages the patrol points. It allows adding patrol points and provides methods to retrieve them.

using System.Collections.Generic;
using UnityEngine;

public class PatrolRoute : MonoBehaviour
{
    private List<Vector3> patrolPoints = new List<Vector3>();

    // Adds a point to the patrol route
    public void AddPatrolPoint(Vector3 point)
    {
        patrolPoints.Add(point);
    }

    // Returns the patrol point at the specified index
    public Vector3 GetPatrolPoint(int index)
    {
        if (index < 0 || index >= patrolPoints.Count)
        {
            return Vector3.zero; // Invalid index check
        }
        return patrolPoints[index];
    }

    // Returns the number of patrol points in the route
    public int GetPatrolPointCount()
    {
        return patrolPoints.Count;
    }

    // Adds the position of a Transform object to the patrol route
    public void AddTransform(Transform point)
    {
        patrolPoints.Add(point.position);
    }
}

2. PatrolIterator.cs

This class implements the iterator for the patrol route, allowing sequential access to the patrol points.

using UnityEngine;

public class PatrolIterator 
{
    private PatrolRoute patrolRoute;
    private int currentIndex = 0;
    
    public PatrolIterator(PatrolRoute route)
    {
        this.patrolRoute = route;
    }

    // Checks if there is another patrol point to visit
    public bool HasNext()
    {
        return currentIndex < patrolRoute.GetPatrolPointCount();
    }

    // Returns the current patrol point and advances the iterator
    public Vector3 Next()
    {
        if (!HasNext()) return Vector3.zero;
        return patrolRoute.GetPatrolPoint(currentIndex);
    }

    // Move to the next point in the patrol route
    public void MoveNext()
    {
        if (HasNext())
        {
            currentIndex++;
        }
    }

    // Reset the iterator to the beginning of the patrol route
    public void Reset()
    {
        currentIndex = 0;
    }
}

3. NPCController.cs

This class controls the NPC's behavior, moving it between patrol points using the iterator.

using UnityEngine;

public class NPCController : MonoBehaviour
{
    public PatrolRoute patrolRoute; // Reference to the patrol route
    private PatrolIterator patrolIterator; // Iterator for the patrol route
    public float speed = 2f; // Speed at which the NPC moves between points

    private Vector3 currentTarget; // The current target patrol point

    private void Start()
    {
        // Add patrol points by finding specific GameObjects in the scene
        patrolRoute.AddTransform(GameObject.Find("Point1").transform);
        patrolRoute.AddTransform(GameObject.Find("Point2").transform);
        patrolRoute.AddTransform(GameObject.Find("Point3").transform);
        patrolRoute.AddTransform(GameObject.Find("Point4").transform);

        patrolIterator = new PatrolIterator(patrolRoute); // Create an iterator for the patrol route
        GoToNextPatrolPoint(); // Set the first target patrol point
    }

    private void Update() => Patrol(); // Call Patrol method every frame

    // Method that moves the NPC towards the current patrol point
    private void Patrol()
    {
        if (patrolIterator.HasNext())
        {
            float step = speed * Time.deltaTime; // Calculate movement step based on speed
            transform.position = Vector3.MoveTowards(transform.position, currentTarget, step); // Move NPC

            // Check if NPC reached the patrol point
            if (Vector3.Distance(transform.position, currentTarget) < 0.1f)
            {
                patrolIterator.MoveNext(); // Move to the next patrol point
                GoToNextPatrolPoint(); // Update current target
            }
        }
        else
        {
            patrolIterator.Reset(); // All points visited, reset the iterator
        }
    }

    // Method to update the NPC's target to the next patrol point
    private void GoToNextPatrolPoint()
    {
        if (patrolIterator.HasNext())
        {
            currentTarget = patrolIterator.Next();
        }
    }
}