1.介绍

热重载是在 Editor 打开的状态下创建或编辑脚本并立即应用脚本行为的过程。无需重新启动应用程序和 Editor 即可使更改生效。更改并保存脚本时，Unity 会热重载所有当前加载的脚本数据。

2.实现原理

1.OperaComponentUpdateSystem.cs

点击R重新装载Logic_.dl,Logic_pdb

            if (Input.GetKeyDown(KeyCode.R))
            {
                //重新读取"Codes/Hotfix/","Codes/HotfixView/"目录打出来的dll,pdb
                CodeLoader.Instance.LoadHotfix();
                //将重新读取的反射类型添加到EventSystem
                Game.EventSystem.Add(CodeLoader.Instance.GetTypes());
                //重新装载反射
                Game.EventSystem.Load();
                Log.Debug("hot reload success!");
            }

2.BuildAssemblieEditor.cs

编译dll

        [MenuItem("Tools/BuildData _F7")]
        public static void BuildData()
        {
            //编译Model/ModelView下的cs为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}";
            //编译Hotfix/HotfixView下的cs为Logic_.dll/pdb
            BuildAssemblieEditor.BuildMuteAssembly(logicFile, new []
            {
                "Codes/Hotfix/",
                "Codes/HotfixView/",
            }, new[]{Path.Combine(Define.BuildOutputDir, "Data.dll")}, CodeOptimization.Debug);
        }

3.?CodeLoader.cs

?重新读取"Codes/Hotfix/","Codes/HotfixView/"目录打出来的dll,pdb

               
		public void LoadHotfix()
		{
			// Unity在这里搞了个优化，认为同一个路径的dll，返回的程序集就一样。所以这里每次编译都要随机名字
			string[] logicFiles = Directory.GetFiles(Define.BuildOutputDir, "Logic_*.dll");
			if (logicFiles.Length != 1)
			{
				throw new Exception("Logic dll count != 1");
			}
			//读取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);

			//将data.dll和logic_.dll的反射类型保存给allTypes变量
			List<Type> listType = new List<Type>();
			listType.AddRange(this.assembly.GetTypes());
			listType.AddRange(hotfixAssembly.GetTypes());
			this.allTypes = listType.ToArray();
		}

4.EventSystem.cs

重新加载dll的反射类型，并重新调用所有loaders队列中的实体的loadsystem类的run方法

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

            this.types.Clear();
            //获取所有继承BaseAttribute的类型
            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;
                    }
                    //将同类型的特性存在一个字典
                    this.types.Add(baseAttributeType, type);
                }
            }

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

                if (obj is ISystemType iSystemType)
                {
                    //将每个类打上ObjectSystem标签的类存字典
                    OneTypeSystems oneTypeSystems = this.typeSystems.GetOrCreateOneTypeSystems(iSystemType.Type());
                    oneTypeSystems.Add(iSystemType.SystemType(), obj);
                }
            }

            this.allEvents.Clear();
            //遍历所有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>());
                }
                //将同一个eventType的类存入allEvents字典
                this.allEvents[eventType].Add(obj);
            }
        }

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

                if (component.IsDisposed)
                {
                    continue;
                }

                //获得entity继承ILoadSystem的类
                List<object> iLoadSystems = this.typeSystems.GetSystems(component.GetType(), typeof (ILoadSystem));
                if (iLoadSystems == null)
                {
                    continue;
                }
                //loaders取出的instanceId压入loaders2
                this.loaders2.Enqueue(instanceId);

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