port from perforce

intromat/NodeNetwork/NNViewRegistrar.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+using NodeNetwork.ViewModels;
+using NodeNetwork.Views;
+using ReactiveUI;
+using Splat;
+
+namespace NodeNetwork
+{
+    /// <summary>
+    /// A locator is used to find the correct view corresponding to a viewmodel.
+    /// In ReactiveUI, usually Splat is used, but others exist. This class acts as an intermediate registrar.
+    /// It gathers registrations and registers them to the preferred locator.
+    /// </summary>
+    public sealed class NNViewRegistrar
+    {
+        private static readonly List<Tuple<Func<object>, Type>> PendingRegistrations = new List<Tuple<Func<object>, Type>>();
+        private static Action<Func<object>, Type> _registerAction;
+
+        public static void AddRegistration(Func<object> factory, Type serviceType)
+        {
+            if (factory == null)
+            {
+                throw new ArgumentNullException(nameof(factory));
+            }
+            else if (serviceType == null)
+            {
+                throw new ArgumentNullException(nameof(serviceType));
+            }
+
+            if (_registerAction == null)
+            {
+                PendingRegistrations.Add(Tuple.Create(factory, serviceType));
+            }
+            else
+            {
+                _registerAction(factory, serviceType);
+            }
+        }
+
+        public static void RegisterToLocator(Action<Func<object>, Type> newRegisterAction)
+        {
+            if (newRegisterAction == null)
+            {
+                throw new ArgumentNullException(nameof(newRegisterAction));
+            }
+            else if (_registerAction != null)
+            {
+                throw new InvalidOperationException("A locator has already been set");
+            }
+
+            _registerAction = newRegisterAction;
+            foreach (var t in PendingRegistrations)
+            {
+                _registerAction(t.Item1, t.Item2);
+            }
+            PendingRegistrations.Clear();
+        }
+
+        /// <summary>
+        /// Register all NodeNetwork view/viewmodel pairs to Locator.CurrentMutable.
+        /// </summary>
+        public static void RegisterSplat()
+        {
+            RegisterToLocator((f, t) => Locator.CurrentMutable.Register(f, t));
+        }
+    }
+}