4-8 Centralizing Special Ability Code

這次重構要將Player內的技能系統分離出來。首先將Energy的名稱改為SpecialAbilities，以後技能設定跟發動將統一放在這邊。

改名以後，Player原本放置Energy的地方會顯示Nothing Selected，請刪除。

重新加入SpecialAbilities。

接著，我們將AbilityConfig.cs中的struct AbilityParams刪除，這個物件太複雜了，而且傳入的參數中包含Enemy，使得我們的技能系統程式侷限在Player攻擊Enemy上，無法讓Enemy也共用技能系統。

刪除以後，會發現使用到AbilityParams的程式碼出現了紅字，請大家統一改成GameObject target。往後被指定攻擊的target可以是Player，也可以是Enemy。

以下列出修改後的SpecialAbilities，Player，AbilityBehaviour。
SpecialAbilities.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using RPG.CameraUI;

namespace RPG.Character{
 public class SpecialAbilities : MonoBehaviour {

  [SerializeField] Image energyOrb;
  [SerializeField] float maxEnergyPoints = 100f;
  [SerializeField] float regenPointPerSecond = 1f;

  [SerializeField] AbilityConfig[] abilities;

  float currentEnergyPoints;
  AbilityBehaviour[] abilityBehaviour;

  float energyAsPersent{ get { return currentEnergyPoints / maxEnergyPoints; }}

  void Start () {
   currentEnergyPoints = maxEnergyPoints;
   AttachSpecialAbility();
  }

  void Update(){
   if (currentEnergyPoints < maxEnergyPoints) {
    AddEnergyPoint ();
    UpdateEnergyBar ();
   }
  }

  private void AttachSpecialAbility(){
   abilityBehaviour = new AbilityBehaviour[abilities.Length];
   for (int i = 0; i < abilities.Length; i++) {
    // 儲存ISpecialAbility物件
    abilityBehaviour[i] = abilities [i].AttachAbilityTo (gameObject);
   }
  }

  public void AttemptSpecialAbility(int abilityIndex, GameObject target = null){
   // 取得技能需要的能量消耗量
   float energyCost = abilities [abilityIndex].GetEnergyCost ();

   if (energyCost <= currentEnergyPoints) {
    ConsumeEnergy (energyCost);
    // 發動技能，並傳入被鎖定的敵人
    abilityBehaviour [abilityIndex].Use(target);
   }
  }

  public float GetNumberOfAbilities(){
   return abilities.Length;
  }

  private void AddEnergyPoint(){
   // 每秒自動恢復能量，由於Update是每個Frame都會執行，故須使用deltaTime取得Frame的間隔時間
   float pointsToAdd = regenPointPerSecond * Time.deltaTime;
   currentEnergyPoints = Mathf.Clamp (currentEnergyPoints + pointsToAdd, 0, maxEnergyPoints);
  }

  // 消耗的魔力由SpecialAbilityConfig決定，傳到amount
  public void ConsumeEnergy(float amount){
   float newEnergyPoint = currentEnergyPoints - amount;
   currentEnergyPoints = Mathf.Clamp (newEnergyPoint, 0, maxEnergyPoints);
   UpdateEnergyBar ();
  }

  void UpdateEnergyBar(){
   energyOrb.fillAmount = energyAsPersent;
  }
 }
}

Player.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Assertions;
using UnityEngine.SceneManagement;
using RPG.CameraUI; // TODO consider re-wiring
using RPG.Core;
using RPG.Weapons;

namespace RPG.Character{
 public class Player : MonoBehaviour {

  [SerializeField] float baseDamage = 50f;
  [SerializeField] AnimatorOverrideController animatorOverrideController;
  [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;
  float currentHealthPoint;
  Enemy currentEnemy;
  CameraRaycaster cameraRaycaster;
  Animator animator;
  SpecialAbilities abilities;
  GameObject weaponInUse;

  void Start(){
   abilities = GetComponent ();

   RegisterForMouseClcik ();
   PutWeaponInHand (currentWeaponConfig);
   OverrideAnimatorController ();
  }

  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 OverrideAnimatorController(){
   // 取得Animator物件
   animator = GetComponent ();
   // 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;
  }

  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 RegisterForMouseClcik(){
   cameraRaycaster = FindObjectOfType ();
   // 註冊滑鼠碰到敵人的事件
   cameraRaycaster.onMouseOverEnemy += OnMouseOverEnemy;
  }

  void OnMouseOverEnemy(Enemy enemy){
   currentEnemy = enemy;

   if (Input.GetMouseButtonDown (0) && IsTargetInRange (enemy.gameObject)) {
    AttackTarget ();
   }else if (Input.GetMouseButtonDown (1)) {
    // 0為使用第一個技能 
    abilities.AttemptSpecialAbility(0, currentEnemy.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
    currentEnemy.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;
   }
  }

  // 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 <= currentWeaponConfig.GetMaxAttackRange();
  }
 }
}

AbilityBehaviour.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

namespace RPG.Character{
 public abstract class AbilityBehaviour : MonoBehaviour {

  protected AbilityConfig config;

  const float PARTICLE_CLEAN_UP_DELAY = 20f;

  public abstract void Use(GameObject target = null);

  public void SetConfig(AbilityConfig config){
   this.config = config;
  }

  protected void PlayEffectAudio(){
   // 取得音效Component
   AudioSource myAudioSource = GetComponent();
   // 從config取得技能音效
   AudioClip audioClip = config.GetAudioClip ();
   // 使用PlayOnShot播放技能音效，可避免和其他技能音效重疊在一起
   myAudioSource.PlayOneShot (audioClip);
  }

  protected void PlayParticleEffect(){
   // 初始化粒子系統，綁定到『自己』身上
   GameObject particlePrefab = Instantiate(config.GetParticlePrefab(),
    transform.position,
    Quaternion.identity,
    transform);
   // 啟動粒子系統
   particlePrefab.GetComponent().Play();
   // 播放完後自我銷毀
   StartCoroutine(DestroyParticleWhenFinished(particlePrefab));
  }

  protected void PlayParticleEffectOnTarget(GameObject target){
   // 初始化粒子系統，綁定到『目標』身上
   GameObject particlePrefab = Instantiate(config.GetParticlePrefab(),
    target.transform.position,
    Quaternion.identity,
    target.transform);
   // 啟動粒子系統
   particlePrefab.GetComponent().Play();
   // 播放完後自我銷毀
   StartCoroutine(DestroyParticleWhenFinished(particlePrefab));
  }

  IEnumerator DestroyParticleWhenFinished(GameObject particlePrefab){
   while (particlePrefab.GetComponent ().isPlaying) {
    yield return new WaitForSeconds (PARTICLE_CLEAN_UP_DELAY);
   }
   Destroy (particlePrefab);
   yield return new WaitForEndOfFrame ();
  }
 }
}

重構完成後，大家可以看見成功將血量跟技能從Player分離出來，分別為Health System與Special Abilities，這兩個組件也能給Enemy使用。