Add Transients/Factories to Dependency Injection

src/Discord.Net.Commands/Dependencies/DependencyMap.cs

@@ -5,21 +5,29 @@ namespace Discord.Commands
 {
     public class DependencyMap : IDependencyMap
     {
-        private Dictionary<Type, object> map;
+        private Dictionary<Type, Func<object>> map;
 
         public static DependencyMap Empty => new DependencyMap();
 
         public DependencyMap()
         {
-            map = new Dictionary<Type, object>();
+            map = new Dictionary<Type, Func<object>>();
         }
 
-        public void Add<T>(T obj)
+        public void Add<T>(T obj) where T : class 
+            => AddFactory(() => obj);
+        public void AddTransient<T>() where T : class, new() 
+            => AddFactory(() => new T());
+        public void AddTransient<TKey, TImpl>() where TKey : class 
+            where TImpl : class, TKey, new() 
+            => AddFactory<TKey>(() => new TImpl());
+
+        public void AddFactory<T>(Func<T> factory) where T : class
         {
             var t = typeof(T);
             if (map.ContainsKey(t))
                 throw new InvalidOperationException($"The dependency map already contains \"{t.FullName}\"");
-            map.Add(t, obj);
+            map.Add(t, factory);
         }
 
         public T Get<T>()
@@ -51,7 +59,14 @@ namespace Discord.Commands
         }
         public bool TryGet(Type t, out object result)
         {
-            return map.TryGetValue(t, out result);
+            Func<object> func;
+            if (map.TryGetValue(t, out func))
+            {
+                result = func();
+                return true;
+            }
+            result = null;
+            return false;
         }
     }
 }

src/Discord.Net.Commands/Dependencies/IDependencyMap.cs

@@ -4,7 +4,10 @@ namespace Discord.Commands
 {
     public interface IDependencyMap
     {
-        void Add<T>(T obj);
+        void Add<T>(T obj) where T : class;
+        void AddTransient<T>() where T : class, new();
+        void AddTransient<TKey, TImpl>() where TKey: class where TImpl : class, TKey, new();
+        void AddFactory<T>(Func<T> factory) where T : class;
 
         T Get<T>();
         bool TryGet<T>(out T result);