using UnityEngine;

public class ComponentAccess : MonoBehaviour
{
    void Start()
    {
        // Get a component on this GameObject
        Rigidbody rb = GetComponent<Rigidbody>();

        // Get a component on a child GameObject
        Collider childCollider = GetComponentInChildren<Collider>();

        // Get all components of a type on this and children
        MeshRenderer[] renderers = GetComponentsInChildren<MeshRenderer>();

        // Add a component at runtime
        BoxCollider box = gameObject.AddComponent<BoxCollider>();

        // Remove a component (destroys it)
        Destroy(box);
    }
}

using UnityEngine;

public class FindingObjects : MonoBehaviour
{
    void Start()
    {
        // Find by tag (returns first match)
        GameObject player = GameObject.FindWithTag("Player");

        // Find all with tag
        GameObject[] enemies = GameObject.FindGameObjectsWithTag("Enemy");

        // Find by name (slow -- avoid in Update)
        GameObject manager = GameObject.Find("GameManager");

        // Compare tags efficiently (no GC allocation)
        if (gameObject.CompareTag("Player"))
        {
            Debug.Log("This is the player");
        }
    }
}

using UnityEngine;

public class InstantiationExample : MonoBehaviour
{
    // Reference to the prefab. Drag a prefab into this field in the Inspector.
    public GameObject myPrefab;

    void Start()
    {
        // Instantiate at position (0, 0, 0) and zero rotation.
        Instantiate(myPrefab, new Vector3(0, 0, 0), Quaternion.identity);
    }
}

using UnityEngine;

public class SpawnWithParent : MonoBehaviour
{
    public GameObject prefab;
    public Transform parentTransform;

    void SpawnChild()
    {
        // Instantiate as child of a parent transform
        GameObject instance = Instantiate(prefab, parentTransform);

        // Instantiate at specific world position under a parent
        GameObject positioned = Instantiate(
            prefab,
            new Vector3(5, 0, 0),
            Quaternion.identity,
            parentTransform
        );
    }
}

using UnityEngine;

[CreateAssetMenu(fileName = "Data", menuName = "ScriptableObjects/SpawnData", order = 1)]
public class SpawnDataScriptableObject : ScriptableObject
{
    public GameObject prefab;
    public int count;
    public Vector3[] positions;
}

using UnityEngine;

public class SpawnManager : MonoBehaviour
{
    public SpawnDataScriptableObject spawnData;

    void Start()
    {
        for (int i = 0; i < spawnData.count; i++)
        {
            Instantiate(spawnData.prefab, spawnData.positions[i], Quaternion.identity);
        }
    }
}

using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneLoader : MonoBehaviour
{
    void Start()
    {
        // Subscribe to scene loaded event
        SceneManager.sceneLoaded += OnSceneLoaded;
    }

    void OnSceneLoaded(Scene scene, LoadSceneMode mode)
    {
        Debug.Log("Loaded: " + scene.name);
    }

    public void LoadLevel(string sceneName)
    {
        // Load scene by name (replaces current)
        SceneManager.LoadScene(sceneName);
    }

    public void LoadAdditive(string sceneName)
    {
        // Load scene additively (keeps current scenes)
        SceneManager.LoadSceneAsync(sceneName, LoadSceneMode.Additive);
    }

    public void UnloadLevel(string sceneName)
    {
        SceneManager.UnloadSceneAsync(sceneName);
    }

    public void GetSceneInfo()
    {
        Scene active = SceneManager.GetActiveScene();
        Debug.Log("Active scene: " + active.name);
        Debug.Log("Loaded scene count: " + SceneManager.loadedSceneCount);
    }
}

using UnityEngine;

public class RespawnSystem : MonoBehaviour
{
    public GameObject respawnPrefab;
    private GameObject respawn;

    void Update()
    {
        if (respawn == null)
            respawn = GameObject.FindWithTag("Respawn");

        if (respawn != null)
        {
            Instantiate(respawnPrefab, respawn.transform.position,
                respawn.transform.rotation);
        }
    }
}

using UnityEngine;

public class ToggleVisibility : MonoBehaviour
{
    public GameObject target;

    public void Toggle()
    {
        // SetActive controls whether the GameObject is active
        target.SetActive(!target.activeSelf);

        // activeSelf: this object's own active state
        // activeInHierarchy: effective state (considers parent chain)
        Debug.Log("Self: " + target.activeSelf);
        Debug.Log("InHierarchy: " + target.activeInHierarchy);
    }
}

using UnityEngine;

public class LayerRaycast : MonoBehaviour
{
    void Update()
    {
        // Create a layer mask for layer named "Ground"
        int groundLayer = LayerMask.NameToLayer("Ground");
        int layerMask = 1 << groundLayer;

        // Raycast only against the Ground layer
        if (Physics.Raycast(transform.position, Vector3.down, out RaycastHit hit, 100f, layerMask))
        {
            Debug.Log("Hit ground at: " + hit.point);
        }

        // Use GetMask for multiple layers
        int combinedMask = LayerMask.GetMask("Ground", "Water");
        Physics.Raycast(transform.position, Vector3.forward, 50f, combinedMask);
    }
}

// BAD: Find is expensive -- runs every frame with string lookup
void Update()
{
    GameObject player = GameObject.Find("Player"); // Avoid!
}

// GOOD: Cache the reference
private GameObject player;
void Start()
{
    player = GameObject.FindWithTag("Player");
}

// BAD: Every prefab instance duplicates this data
public class EnemyStats : MonoBehaviour
{
    public int health = 100;
    public float speed = 5f;
    public string enemyName = "Goblin";
}

// GOOD: Use a ScriptableObject -- one asset, many references
[CreateAssetMenu(menuName = "ScriptableObjects/EnemyConfig")]
public class EnemyConfig : ScriptableObject
{
    public int health = 100;
    public float speed = 5f;
    public string enemyName = "Goblin";
}

public class Enemy : MonoBehaviour
{
    public EnemyConfig config; // All instances share the same asset
}

// BAD: Changes in Edit mode won't persist
settings.value += 10;

// GOOD: Mark asset dirty so Unity saves it
settings.value += 10;
EditorUtility.SetDirty(settings);

// BAD: Allocates a new string for comparison (GC pressure)
if (gameObject.tag == "Player") { }

// GOOD: CompareTag avoids allocation
if (gameObject.CompareTag("Player")) { }