From 6d273251556a992bbe7e9166e43e515586c9396f Mon Sep 17 00:00:00 2001
From: gered <gered@blarg.ca>
Date: Thu, 22 Aug 2013 12:33:35 -0400
Subject: [PATCH] remove "new()" generic type constraints, mimic using
 reflection

---
 Blarg.GameFramework/Support/ObjectPools.cs | 35 ++++++++++++++++++----
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/Blarg.GameFramework/Support/ObjectPools.cs b/Blarg.GameFramework/Support/ObjectPools.cs
index e84b859..e71d073 100644
--- a/Blarg.GameFramework/Support/ObjectPools.cs
+++ b/Blarg.GameFramework/Support/ObjectPools.cs
@@ -11,40 +11,65 @@ namespace Blarg.GameFramework.Support
 		class ObjectObjectPool : ObjectPool<Object>
 		{
 			Type _type;
+			ConstructorInfo _constructor;
 
-			public ObjectObjectPool(Type type)
+			public ObjectObjectPool(Type type, ConstructorInfo constructor)
 				: base(INITIAL_CAPACITY)
 			{
 				_type = type;
+				_constructor = constructor;
 			}
 
 			protected override object Allocate()
 			{
-				return Activator.CreateInstance(_type);
+				// TODO: use a compiled lambda expression instead?
+				//       need to check if possible when AOT compiled
+				return _constructor.Invoke(null);
 			}
 		}
 
 		static Dictionary<Type, ObjectObjectPool> _pools = new Dictionary<Type, ObjectObjectPool>();
 
+		static ConstructorInfo GetParameterlessConstructor(Type type)
+		{
+			var constructors = type.GetConstructors();
+			for (int i = 0; i < constructors.Length; ++i)
+			{
+				if (constructors[i].GetParameters().Length == 0)
+					return constructors[i];
+			}
+
+			return null;
+		}
+
 		static ObjectObjectPool GetPool(Type type)
 		{
 			ObjectObjectPool pool;
 			_pools.TryGetValue(type, out pool);
 			if (pool == null)
 			{
-				pool = new ObjectObjectPool(type);
+				// why do we do this instead of just using a "new()" generic type constraint?
+				// because doing it this way saves us from having to litter that same type
+				// constraint on every other class method (in other classes) which might be
+				// using ObjectPools to auto manage their object pools. Sometimes it gets
+				// a bit restrictive ...0
+				var constructor = GetParameterlessConstructor(type);
+				if (constructor == null)
+					throw new InvalidOperationException("ObjectPools can only be used for types with parameterless constructors.");
+
+				pool = new ObjectObjectPool(type, constructor);
 				_pools.Add(type, pool);
 			}
 			return pool;
 		}
 
-		public static T Take<T>() where T : class, new()
+		public static T Take<T>() where T : class
 		{
 			var pool = GetPool(typeof(T));
 			return (T)pool.Take();
 		}
 
-		public static void Free<T>(T obj) where T : class, new()
+		public static void Free<T>(T obj) where T : class
 		{
 			var pool = GetPool(typeof(T));
 			pool.Free(obj);