1.介紹

熱多載是在 Editor 打開的狀態下創建或編輯腳本并立即應用腳本行為的程序，無需重新啟動應用程式和 Editor 即可使更改生效，更改并保存腳本時，Unity 會熱多載所有當前加載的腳本資料，

2.實作原理

1.OperaComponentUpdateSystem.cs

點擊R重新裝載Logic_.dl,Logic_pdb

            if (Input.GetKeyDown(KeyCode.R))
            {
                //重新讀取"Codes/Hotfix/","Codes/HotfixView/"目錄打出來的dll,pdb
                CodeLoader.Instance.LoadHotfix();
                //將重新讀取的反射型別添加到EventSystem
                Game.EventSystem.Add(CodeLoader.Instance.GetTypes());
                //重新裝載反射
                Game.EventSystem.Load();
                Log.Debug("hot reload success!");
            }

2.BuildAssemblieEditor.cs

編譯dll

        [MenuItem("Tools/BuildData _F7")]
        public static void BuildData()
        {
            //編譯Model/ModelView下的cs為data.dll/pdb
            BuildAssemblieEditor.BuildMuteAssembly("Data", new []
            {
                "Codes/Model/",
                "Codes/ModelView/",
            }, Array.Empty<string>(), CodeOptimization.Debug);
        }
        
        
        [MenuItem("Tools/BuildLogic _F8")]
        public static void BuildLogic()
        {
            string[] logicFiles = Directory.GetFiles(Define.BuildOutputDir, "Logic_*");
            foreach (string file in logicFiles)
            {
                File.Delete(file);
            }
            
            int random = RandomHelper.RandomNumber(100000000, 999999999);
            string logicFile = $"Logic_{random}";
            //編譯Hotfix/HotfixView下的cs為Logic_.dll/pdb
            BuildAssemblieEditor.BuildMuteAssembly(logicFile, new []
            {
                "Codes/Hotfix/",
                "Codes/HotfixView/",
            }, new[]{Path.Combine(Define.BuildOutputDir, "Data.dll")}, CodeOptimization.Debug);
        }

3. CodeLoader.cs

重新讀取"Codes/Hotfix/","Codes/HotfixView/"目錄打出來的dll,pdb

               
		public void LoadHotfix()
		{
			// Unity在這里搞了個優化，認為同一個路徑的dll，回傳的程式集就一樣，所以這里每次編譯都要隨機名字
			string[] logicFiles = Directory.GetFiles(Define.BuildOutputDir, "Logic_*.dll");
			if (logicFiles.Length != 1)
			{
				throw new Exception("Logic dll count != 1");
			}
			//讀取logic_.dll/pdb
			string logicName = Path.GetFileNameWithoutExtension(logicFiles[0]);
			byte[] assBytes = File.ReadAllBytes(Path.Combine(Define.BuildOutputDir, $"{logicName}.dll"));
			byte[] pdbBytes = File.ReadAllBytes(Path.Combine(Define.BuildOutputDir, $"{logicName}.pdb"));

			Assembly hotfixAssembly = Assembly.Load(assBytes, pdbBytes);

			//將data.dll和logic_.dll的反射型別保存給allTypes變數
			List<Type> listType = new List<Type>();
			listType.AddRange(this.assembly.GetTypes());
			listType.AddRange(hotfixAssembly.GetTypes());
			this.allTypes = listType.ToArray();
		}

4.EventSystem.cs

重新加載dll的反射型別，并重新呼叫所有loaders佇列中的物體的loadsystem類的run方法

            public void Add(Type[] addTypes)
            {
            this.allTypes.Clear();
            foreach (Type addType in addTypes)
            {
                this.allTypes[addType.FullName] = addType;
            }

            this.types.Clear();
            //獲取所有繼承BaseAttribute的型別
            List<Type> baseAttributeTypes = GetBaseAttributes(addTypes);
            foreach (Type baseAttributeType in baseAttributeTypes)
            {
                foreach (Type type in addTypes)
                {
                    if (type.IsAbstract)
                    {
                        continue;
                    }

                    object[] objects = type.GetCustomAttributes(baseAttributeType, true);
                    if (objects.Length == 0)
                    {
                        continue;
                    }
                    //將同型別的特性存在一個字典
                    this.types.Add(baseAttributeType, type);
                }
            }

            this.typeSystems = new TypeSystems();
            //遍歷所有ObjectSystemAttribute
            foreach (Type type in this.GetTypes(typeof (ObjectSystemAttribute)))
            {
                object obj = Activator.CreateInstance(type);

                if (obj is ISystemType iSystemType)
                {
                    //將每個類打上ObjectSystem標簽的類存字典
                    OneTypeSystems oneTypeSystems = this.typeSystems.GetOrCreateOneTypeSystems(iSystemType.Type());
                    oneTypeSystems.Add(iSystemType.SystemType(), obj);
                }
            }

            this.allEvents.Clear();
            //遍歷所有EventAttribute
            foreach (Type type in types[typeof (EventAttribute)])
            {
                IEvent obj = Activator.CreateInstance(type) as IEvent;
                if (obj == null)
                {
                    throw new Exception($"type not is AEvent: {obj.GetType().Name}");
                }

                Type eventType = obj.GetEventType();
                if (!this.allEvents.ContainsKey(eventType))
                {
                    this.allEvents.Add(eventType, new List<object>());
                }
                //將同一個eventType的類存入allEvents字典
                this.allEvents[eventType].Add(obj);
            }
        }

        public void Load()
        {
            while (this.loaders.Count > 0)
            {
                //取到loaders佇列的entity
                long instanceId = this.loaders.Dequeue();
                Entity component;
                if (!this.allEntities.TryGetValue(instanceId, out component))
                {
                    continue;
                }

                if (component.IsDisposed)
                {
                    continue;
                }

                //獲得entity繼承ILoadSystem的類
                List<object> iLoadSystems = this.typeSystems.GetSystems(component.GetType(), typeof (ILoadSystem));
                if (iLoadSystems == null)
                {
                    continue;
                }
                //loaders取出的instanceId壓入loaders2
                this.loaders2.Enqueue(instanceId);

                foreach (ILoadSystem iLoadSystem in iLoadSystems)
                {
                    try
                    {
                        //運行load方法
                        iLoadSystem.Run(component);
                    }
                    catch (Exception e)
                    {
                        Log.Error(e);
                    }
                }
            }
            //將loaders和loaders2交換，方便下次使用
            ObjectHelper.Swap(ref this.loaders, ref this.loaders2);
        }

3.熱多載的使用

1.運行前按F7,F8編譯data.dll和logic_.dll

2.運行中修改"Codes/Hotfix/","Codes/HotfixView/"目錄下的代碼時按F8然后R就能實作熱多載

3.建議物體的初始化方法封裝一個函式，在AwakeSystem呼叫的，然后也要寫個LoadSystem呼叫該初始化方法，才可以實作物體的初始化重繪熱多載