4-11 Extracting WeaponSystem

今天的重構要來分離PlayerMovement中的武器設定到WeaponSystem，包含攻擊、致命一擊、更換武器等功能，如此一來，往後的Enemy也能夠裝上武器系統了呢，就能讓Enemy的手中套用武器跟攻擊動作了！

首先，我在Character新增了一個Base Script資料夾，往後不管是Player, Enemy, NPC等角色都能到此資料夾選擇加裝不同的系統。然後請大家新增一個Script名為WeaponSystem。

如下圖為重構完成後的WeaponSystem，大家應該能夠從參數中看出來本次要從PlayerMovement中移動哪些程式碼到WeaponSystem吧，可以先自行試試看唷。

以下提供修改好的PlayerMovement與WeaponSystem程式碼。
PlayerMovement：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
using RPG.CameraUI;
using RPG.Core;
using RPG.Weapons;

namespace RPG.Character{
 public class PlayerMovement : MonoBehaviour {

  [SerializeField] float walkMoveStopRadius = 0.2f;
  [SerializeField] float attackMoveStopRadius = 5f;

  float currentHealthPoint;
  Enemy currentEnemy;
  Character character;
  SpecialAbilities abilities;
  WeaponSystem weaponSystem;

  void Start(){
   abilities = GetComponent ();
   character = GetComponent ();
   weaponSystem = GetComponent ();

   RegisterForMouseClcik ();
  }

  void Update(){
   float healthAsPercentage = GetComponent ().healthAsPercentage;
   if (healthAsPercentage > Mathf.Epsilon) {
    ScanForAbilityKeyDown ();
   }
  }

  private void ScanForAbilityKeyDown(){
   for (int keyIndex = 1; keyIndex <= abilities.GetNumberOfAbilities(); keyIndex++) {
    if (Input.GetKeyDown (keyIndex.ToString())) {
     if (currentEnemy) {
      abilities.AttemptSpecialAbility (keyIndex, currentEnemy.gameObject);
     } else {
      abilities.AttemptSpecialAbility (keyIndex);
     }
    }
   }
  }

  private void RegisterForMouseClcik(){
   CameraRaycaster cameraRaycaster = FindObjectOfType ();
   cameraRaycaster.onMouseOverEnemy += OnMouseOverEnemy;
   cameraRaycaster.onMouseOverWalkable += OnMouseOverWalkable;
  }

  void OnMouseOverEnemy(Enemy enemy){
   currentEnemy = enemy;

   if (Input.GetMouseButton (0)) {
    // 設置地點為Enemy的位置
    character.SetDestination(enemy.transform.position);
    character.SetStopDistance(attackMoveStopRadius);
    if (IsTargetInRange (enemy.gameObject)) {
     weaponSystem.AttackTarget (enemy.gameObject);
    }
   } else if (Input.GetMouseButtonDown (1)) {
    // 0為使用第一個技能 
    abilities.AttemptSpecialAbility(0, currentEnemy.gameObject);
   }
  }

  void OnMouseOverWalkable(Vector3 destination){
   if (Input.GetMouseButton (0)) {
    // 設置地點為滑鼠點擊的位置
    character.SetDestination(destination);
    character.SetStopDistance (walkMoveStopRadius);
   }
  }

  // 確認敵人是否在範圍技的攻擊範圍內
  private bool IsTargetInRange(GameObject target){
   float distanceToTarget = (target.transform.position - transform.position).magnitude;
   return distanceToTarget <= weaponSystem.GetCurrentWeapon().GetMaxAttackRange();
  }

  void OnDrawGizmos(){
   //繪製攻擊範圍
   Gizmos.color = new Color(255f, 0f, 0f, 0.5f);
   Gizmos.DrawWireSphere (transform.position, attackMoveStopRadius);
  }
 }
}

WeaponSystem：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Assertions;
using RPG.Weapons;

namespace RPG.Character{
 public class WeaponSystem : MonoBehaviour {

  [SerializeField] float baseDamage = 50f;
  [SerializeField] Weapon currentWeaponConfig;
  [Range(.1f, 1.0f)] [SerializeField] float criticalHitChance = 0.1f;
  [SerializeField] float criticalHitMultiplier = 2.5f;
  [SerializeField] ParticleSystem criticalHitParticle;

  // 定義Trigger的字串常數
  const string ATTACK_TRIGGER = "Attack";
  const string DEFAULT_ATTACK = "DEFAULT ATTACK";

  float lastHitTime;
  GameObject weaponInUse;
  GameObject target;
  Character character;
  Animator animator;

  void Start () {
   animator = GetComponent ();
   character = GetComponent ();

   PutWeaponInHand (currentWeaponConfig);
   OverrideAnimatorController ();
  }
  
  void Update () {
   
  }

  private void OverrideAnimatorController(){
   AnimatorOverrideController animatorOverrideController = 
    character.GetOverrideController ();
   // 將人物的Animator取代為我們剛剛新增的Player Animator Override
   animator.runtimeAnimatorController = animatorOverrideController;
   // Player Animator Override中有一預設的DEFAULT ATTACK，將其取代成Weapon物件中的Animation
   // 亦即人物的Animation將會依據不同的Weapon物件，而使用有不同的動畫
   animatorOverrideController [DEFAULT_ATTACK] = currentWeaponConfig.GetAnimClip ();
  }

  public void PutWeaponInHand(Weapon weaponToUse){
   currentWeaponConfig = weaponToUse;
   // 先移除之前手持的武器
   Destroy(weaponInUse);
   GameObject weaponPrefab = weaponToUse.GetWeaponPrefab ();
   // 生成武器時，將會放置到指定的GameObject之下，此處為WeaponSocket之下
   // 故可將WeaponSocket設置成玩家的右手或左手
   GameObject weaponSocket = RequestDominantHand();
   weaponInUse = Instantiate (weaponPrefab, weaponSocket.transform);
   // 將武器放置到正確的位置，並有正確的方向
   weaponInUse.transform.localPosition = currentWeaponConfig.gripTransform.localPosition;
   weaponInUse.transform.localRotation = currentWeaponConfig.gripTransform.localRotation;
  }

  public void AttackTarget(GameObject targetToAttack){
   target = targetToAttack;
   AttackTarget ();
  }

  public Weapon GetCurrentWeapon(){
   return currentWeaponConfig;
  }

  private GameObject RequestDominantHand(){
   // 從Children中尋找包含DominantHand的物件
   DominantHand[] dominantHand = GetComponentsInChildren ();
   // 計算取得有DominantHand的物件的數量
   int numberOfDominantHands = dominantHand.Length;
   // 確保該數量不為0
   Assert.AreNotEqual (numberOfDominantHands, 0, "No DominantHand found on player, please add one");
   // 確保該數量不要大於1
   Assert.IsFalse (numberOfDominantHands > 1, "Multiple Dominant script on Player, please remove one");
   // 傳回屬於該DominantHand的GameObject
   return dominantHand [0].gameObject;
  }

  private void AttackTarget(){
   // 確認本次攻擊時間離上一次攻擊時間須大於minTimeBetweenHits，相當於技能冷卻時間
   if ( (Time.time - lastHitTime > currentWeaponConfig.GetMinTimeBetweenHits())) {
    // 每次攻擊前都重設武器的攻擊動畫
    OverrideAnimatorController();
    // 呼叫Trigger啟動攻擊動畫
    animator.SetTrigger(ATTACK_TRIGGER);
    // 呼叫攻擊Target的方法
    target.GetComponent().TakeDamage(CalculateDamage());
    // 紀錄目前攻擊的時間
    lastHitTime = Time.time;
   }
  }

  private float CalculateDamage(){
   // 產生隨機值，比較該值是否小於致命一擊的機率
   bool isCriticalHit = Random.Range (0f, 1f) <= criticalHitChance;
   float damageBeforeCritical = baseDamage + currentWeaponConfig.GetAdditionalDamage ();
   if (isCriticalHit) {
    // 播放致命一擊的特效
    criticalHitParticle.Play ();
    // 回傳攻擊力乘上致命一擊的乘率
    return damageBeforeCritical * criticalHitMultiplier;
   } else {
    return damageBeforeCritical;
   }
  }
 }
}

修改完成後，讓我們試看看套用到Enemy身上吧。首先我找出Enemy放置武器的位置。

接著在該位置新增Dominant Hand組件。

並替該Enemy新增Weapon System，設定好相關武器跟參數。

執行遊戲看看，哇！連Enemy都拿起鋤頭了！