Adding DIScope - an implementation of dependency injection container pattern

Author: pdeschain

Assets/BossRoom/Scripts/Shared/Infrastructure.meta

@@ -0,0 +1,333 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using UnityEngine;
+
+namespace BossRoom.Scripts.Shared.Infrastructure
+{
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor)]
+    public sealed class Inject : Attribute
+    {
+    }
+
+    public class NoInstanceToInjectException : Exception
+    {
+        public NoInstanceToInjectException(string message) : base(message)
+        {
+        }
+    }
+
+    public class ScopeNotFinalizedException : Exception
+    {
+        public ScopeNotFinalizedException(string message) : base(message)
+        {
+        }
+    }
+
+    public interface IInstanceResolver
+    {
+        T Resolve<T>()
+            where T : class;
+
+        void InjectIn(object obj);
+        void InjectIn(GameObject obj);
+    }
+
+    public sealed class DIScope : IInstanceResolver, IDisposable
+    {
+        private static DIScope m_rootScope;
+
+        private readonly DisposableGroup m_DisposableGroup = new DisposableGroup();
+        private readonly Dictionary<Type, LazyBindDescriptor> m_LazyBindDescriptors = new Dictionary<Type, LazyBindDescriptor>();
+
+        private readonly DIScope m_Parent;
+        private readonly Dictionary<Type, object> m_TypesToInstances = new Dictionary<Type, object>();
+        private bool m_Disposed;
+
+        private bool m_ScopeConstructionComplete;
+
+        public DIScope(DIScope parent = null)
+        {
+            m_Parent = parent;
+            BindInstanceAsSingle<IInstanceResolver, DIScope>(this);
+        }
+
+        public static DIScope RootScope
+        {
+            get
+            {
+                if (m_rootScope == null) m_rootScope = new DIScope();
+
+                return m_rootScope;
+            }
+        }
+
+        public void Dispose()
+        {
+            if (!m_Disposed)
+            {
+                m_TypesToInstances.Clear();
+                m_DisposableGroup.Dispose();
+                m_Disposed = true;
+            }
+        }
+
+        public T Resolve<T>()
+            where T : class
+        {
+            if (!m_ScopeConstructionComplete)
+                throw new ScopeNotFinalizedException(
+                    $"Trying to Resolve type {typeof(T)}, but the DISCope is not yet finalized! You should call FinalizeScopeConstruction before any of the Resolve calls.");
+            //if we have this type as lazy-bound instance - we are going to instantiate it now
+            if (m_LazyBindDescriptors.TryGetValue(typeof(T), out var lazyBindDescriptor))
+            {
+                var instance = (T) InstantiateLazyBoundObject(lazyBindDescriptor);
+                m_LazyBindDescriptors.Remove(typeof(T));
+                return instance;
+            }
+
+            if (!m_TypesToInstances.TryGetValue(typeof(T), out var value))
+            {
+                if (m_Parent != null) return m_Parent.Resolve<T>();
+
+                throw new NoInstanceToInjectException($"Injection of type {typeof(T)} failed.");
+            }
+
+            return (T) value;
+        }
+
+        public void InjectIn(object obj)
+        {
+            if (CachedReflectionUtility.TryGetInjectableMethod(obj.GetType(), out var injectionMethod))
+            {
+                var parameters = CachedReflectionUtility.GetMethodParameters(injectionMethod);
+
+                var paramColleciton = new object[parameters.Length];
+
+                for (var i = 0; i < parameters.Length; i++)
+                {
+                    var parameter = parameters[i];
+
+                    var genericResolveMethod = CachedReflectionUtility.GetTypedResolveMethod(parameter.ParameterType);
+                    var resolved = genericResolveMethod.Invoke(this, null);
+                    paramColleciton[i] = resolved;
+                }
+
+                injectionMethod.Invoke(obj, paramColleciton);
+            }
+        }
+
+        public void InjectIn(GameObject go)
+        {
+            var components = go.GetComponentsInChildren<Component>();
+
+            foreach (var component in components) InjectIn(component);
+        }
+
+        ~DIScope()
+        {
+            Dispose();
+        }
+
+        public void BindInstanceAsSingle<T>(T instance) where T : class
+        {
+            BindInstanceToType(instance, typeof(T));
+        }
+
+        public void BindInstanceAsSingle<TInterface, TImplementation>(TImplementation instance)
+            where TImplementation : class, TInterface
+            where TInterface : class
+        {
+            BindInstanceAsSingle<TInterface>(instance);
+            BindInstanceAsSingle(instance);
+        }
+
+        private void BindInstanceToType(object instance, Type type)
+        {
+            m_TypesToInstances[type] = instance;
+        }
+
+        public void BindAsSingle<TImplementation, TInterface>()
+            where TImplementation : class, TInterface
+            where TInterface : class
+        {
+            LazyBind(typeof(TImplementation), typeof(TInterface));
+        }
+
+        public void BindAsSingle<TImplementation, TInterface, TInterface2>()
+            where TImplementation : class, TInterface, TInterface2
+            where TInterface : class
+            where TInterface2 : class
+        {
+            LazyBind(typeof(TImplementation), typeof(TInterface), typeof(TInterface2));
+        }
+
+        public void BindAsSingle<T>()
+            where T : class
+        {
+            LazyBind(typeof(T));
+        }
+
+        private void LazyBind(Type type, params Type[] typeAliases)
+        {
+            var descriptor = new LazyBindDescriptor(type, typeAliases);
+
+            foreach (var typeAlias in typeAliases) m_LazyBindDescriptors[typeAlias] = descriptor;
+
+            m_LazyBindDescriptors[type] = descriptor;
+        }
+
+        private object InstantiateLazyBoundObject(LazyBindDescriptor descriptor)
+        {
+            object instance;
+            if (CachedReflectionUtility.TryGetInjectableConstructor(descriptor.Type, out var constructor))
+            {
+                var parameters = GetResolvedInjectionMethodParameters(constructor);
+                instance = constructor.Invoke(parameters);
+            }
+            else
+            {
+                instance = Activator.CreateInstance(descriptor.Type);
+                InjectIn(instance);
+            }
+
+            AddToDisposableGroupIfDisposable(instance);
+
+            BindInstanceToType(instance, descriptor.Type);
+
+            if (descriptor.InterfaceTypes != null)
+                foreach (var interfaceType in descriptor.InterfaceTypes)
+                    BindInstanceToType(instance, interfaceType);
+
+            return instance;
+        }
+
+        private void AddToDisposableGroupIfDisposable(object instance)
+        {
+            if (instance is IDisposable disposable) m_DisposableGroup.Add(disposable);
+        }
+
+        /// <summary>
+        ///     This method forces the finalization of construction of DI Scope. It would inject all the instances passed to it directly.
+        ///     Objects that were bound by just type will be instantiated on their first use.
+        /// </summary>
+        public void FinalizeScopeConstruction()
+        {
+            if (m_ScopeConstructionComplete) return;
+
+            m_ScopeConstructionComplete = true;
+
+            var uniqueObjects = new HashSet<object>(m_TypesToInstances.Values);
+
+            foreach (var objectToInject in uniqueObjects)
+            {
+                InjectIn(objectToInject);
+            }
+        }
+
+        private object[] GetResolvedInjectionMethodParameters(MethodBase injectionMethod)
+        {
+            var parameters = CachedReflectionUtility.GetMethodParameters(injectionMethod);
+
+            var paramColleciton = new object[parameters.Length];
+
+            for (var i = 0; i < parameters.Length; i++)
+            {
+                var parameter = parameters[i];
+
+                var genericResolveMethod = CachedReflectionUtility.GetTypedResolveMethod(parameter.ParameterType);
+                var resolved = genericResolveMethod.Invoke(this, null);
+                paramColleciton[i] = resolved;
+            }
+
+            return paramColleciton;
+        }
+
+        private static class CachedReflectionUtility
+        {
+            private static readonly Dictionary<Type, MethodBase> k_CachedInjectableMethods = new Dictionary<Type, MethodBase>();
+            private static readonly Dictionary<Type, ConstructorInfo> k_CachedInjectableConstructors = new Dictionary<Type, ConstructorInfo>();
+            private static readonly Dictionary<MethodBase, ParameterInfo[]> k_CachedMethodParameters = new Dictionary<MethodBase, ParameterInfo[]>();
+            private static readonly Dictionary<Type, MethodInfo> k_CachedResolveMethods = new Dictionary<Type, MethodInfo>();
+            private static readonly Type k_InjectAttributeType = typeof(Inject);
+            private static readonly HashSet<Type> k_ProcessedTypes = new HashSet<Type>();
+            private static MethodInfo k_ResolveMethod;
+
+            public static bool TryGetInjectableConstructor(Type type, out ConstructorInfo method)
+            {
+                CacheTypeMethods(type);
+                return k_CachedInjectableConstructors.TryGetValue(type, out method);
+            }
+
+            private static void CacheTypeMethods(Type type)
+            {
+                if (k_ProcessedTypes.Contains(type)) return;
+
+                var constructors = type.GetConstructors();
+                foreach (var constructorInfo in constructors)
+                {
+                    var foundInjectionSite = constructorInfo.IsDefined(k_InjectAttributeType);
+                    if (foundInjectionSite)
+                    {
+                        k_CachedInjectableConstructors[type] = constructorInfo;
+                        var methodParameters = constructorInfo.GetParameters();
+                        k_CachedMethodParameters[constructorInfo] = methodParameters;
+                        break;
+                    }
+                }
+
+                var methods = type.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
+
+                foreach (var methodInfo in methods)
+                {
+                    var foundInjectionSite = methodInfo.IsDefined(k_InjectAttributeType);
+                    if (foundInjectionSite)
+                    {
+                        k_CachedInjectableMethods[type] = methodInfo;
+                        var methodParameters = methodInfo.GetParameters();
+                        k_CachedMethodParameters[methodInfo] = methodParameters;
+                        break;
+                    }
+                }
+
+
+                k_ProcessedTypes.Add(type);
+            }
+
+            public static bool TryGetInjectableMethod(Type type, out MethodBase method)
+            {
+                CacheTypeMethods(type);
+                return k_CachedInjectableMethods.TryGetValue(type, out method);
+            }
+
+            public static ParameterInfo[] GetMethodParameters(MethodBase injectionMethod)
+            {
+                return k_CachedMethodParameters[injectionMethod];
+            }
+
+            public static MethodInfo GetTypedResolveMethod(Type parameterType)
+            {
+                if (!k_CachedResolveMethods.TryGetValue(parameterType, out var resolveMethod))
+                {
+                    if (k_ResolveMethod == null) k_ResolveMethod = typeof(DIScope).GetMethod("Resolve");
+                    resolveMethod = k_ResolveMethod.MakeGenericMethod(parameterType);
+                    k_CachedResolveMethods[parameterType] = resolveMethod;
+                }
+
+                return resolveMethod;
+            }
+        }
+
+        private struct LazyBindDescriptor
+        {
+            public readonly Type Type;
+            public readonly Type[] InterfaceTypes;
+
+            public LazyBindDescriptor(Type type, Type[] interfaceTypes)
+            {
+                Type = type;
+                InterfaceTypes = interfaceTypes;
+            }
+        }
+    }
+}

Assets/BossRoom/Scripts/Shared/Infrastructure/DIScope.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+
+namespace BossRoom.Scripts.Shared.Infrastructure
+{
+    public class DisposableGroup : IDisposable
+    {
+        private readonly List<IDisposable> m_Disposables = new List<IDisposable>();
+
+        public void Dispose()
+        {
+            foreach (var disposable in m_Disposables) disposable.Dispose();
+            m_Disposables.Clear();
+        }
+
+        public void Add(IDisposable disposable)
+        {
+            m_Disposables.Add(disposable);
+        }
+    }
+}