feat(DependencyInjector): add TryProvide method

Core/DependencyInjector.cs

@@ -83,6 +83,19 @@ public T Provide<T>() where T : class
 
             return (T) DependencyDictionary[type];
         }
+
+        public bool TryProvide<T>(out T instance) where T : class
+        {
+            instance = null;
+            var type = typeof(T);
+
+            if (!DependencyDictionary.ContainsKey(type))
+                return false;
+
+            instance = (T) DependencyDictionary[type];
+
+            return true;
+        }
 
         private void PopulateFromDependencyAttributes(IEnumerable<DependencyAttribute> dependencyAttributes)
         {

Tests/DependencyInjectorTests.cs

@@ -30,9 +30,40 @@ public void Throws_If_No_Provider_Exists()
             {
                 var injector = new DependencyInjector();
 
-                Assert.Throws<MissingProviderException>(
+                var exception = Assert.Throws<MissingProviderException>(
                     () => injector.Provide<IDependency>()
                 );
+
+                Assert.That(exception.Message, Is.EqualTo("No provider found for IDependency"));
+            }
+        }
+
+        [TestFixture]
+        public class TryProvide
+        {
+            [Test]
+            public void Returns_If_Dependency_Could_Be_Provided()
+            {
+                var injector = new DependencyInjector();
+
+                Assert.That(injector.TryProvide<IDependency>(out _), Is.False);
+
+                injector.SetDependency<IDependency>(new DependencyOne());
+
+                var wasProvided = injector.TryProvide<IDependency>(out var instance);
+
+                Assert.That(wasProvided, Is.True);
+                Assert.That(instance, Is.InstanceOf<DependencyOne>());
+            }
+
+            [Test]
+            public void Yields_Null_If_Dependency_Can_Not_Be_Provided()
+            {
+                var injector = new DependencyInjector();
+
+                injector.TryProvide<IDependency>(out var instance);
+
+                Assert.That(instance, Is.Null);
             }
         }
 

Tests/UIComponentDependencyTests.cs

@@ -49,16 +49,6 @@ public UIComponentSubclassWithDependencyOverride()
             }
         }
 
-        private class UIComponentWithNoProvider : UIComponent
-        {
-            public readonly IStringDependency StringDependency;
-
-            public UIComponentWithNoProvider()
-            {
-                StringDependency = Provide<IStringDependency>();
-            }
-        }
-
         [Test]
         public void The_Correct_Class_Is_Provided_To_Component()
         {
@@ -72,12 +62,5 @@ public void The_Correct_Class_Is_Provided_To_Component_When_Overridden()
             var component = new UIComponentSubclassWithDependencyOverride();
             Assert.That(component.StringDependency, Is.InstanceOf<EmptyStringProvider>());
         }
-
-        [Test]
-        public void Null_Is_Provided_When_No_Provider_Exists()
-        {
-            var component = new UIComponentWithNoProvider();
-            Assert.That(component.StringDependency, Is.Null);
-        }
     }
 }