Implement passing test for ElementPickerViewModel.

Tests/Tests.csproj

@@ -91,6 +91,7 @@
     <Compile Include="Thesaurus\TestThesaurus.cs" />
     <Compile Include="Importer\ZaaImporter\TimePointTest.cs" />
     <Compile Include="TestHelpers.cs" />
+    <Compile Include="ViewModels\ElementPickerViewModelTest.cs" />
     <Compile Include="ViewModels\SettingsRepositoryViewModelTest.cs" />
     <Compile Include="ViewModels\SettingsViewModelTest.cs" />
   </ItemGroup>

Tests/ViewModels/ElementPickerViewModelTest.cs

@@ -0,0 +1,54 @@
+/* ElementPickerViewModelTest.cs
+ * part of zaaReloaded2
+ * 
+ * Copyright 2015 Daniel Kraus
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using NUnit.Framework;
+using Bovender.Mvvm.ViewModels;
+using zaaReloaded2.ViewModels;
+
+namespace Tests.ViewModels
+{
+    [TestFixture]
+    class ElementPickerViewModelTest
+    {
+        [Test]
+        public void ChooseElement()
+        {
+            ElementPickerViewModel vm = new ElementPickerViewModel(true);
+            ViewModelBase elementVM = vm.Categories.First().Children.First();
+            elementVM.IsSelected = true;
+            string expectedLabel = elementVM.DisplayString;
+
+            Assert.IsTrue(vm.ChooseElementCommand.CanExecute(null),
+                "Cannot execute ChooseElementCommand");
+
+            bool messageSent = false;
+            vm.ElementChosenMessage.Sent += (sender, args) =>
+            {
+                messageSent = true;
+                ViewModelBase messageContentVM = args.Content.ViewModel as ViewModelBase;
+                Assert.AreEqual(expectedLabel, messageContentVM.DisplayString);
+            };
+
+            vm.ChooseElementCommand.Execute(null);
+            Assert.IsTrue(messageSent, "No message was sent when element was chosen");
+        }
+    }
+}

zaaReloaded2/ViewModels/ElementPickerViewModel.cs

@@ -38,19 +38,65 @@ namespace zaaReloaded2.ViewModels
         /// <summary>
         /// A two-dimensional tree 
         /// </summary>
-        public IList<CategoryViewModel> AvailableElements { get; private set; }
+        public IList<CategoryViewModel> Categories { get; private set; }
+
+        /// <summary>
+        /// Gets the currently selected element, or null if no element is selected.
+        /// </summary>
+        /// <remarks>
+        /// TODO: Raise PropertyChanged event.
+        /// </remarks>
+        public ElementViewModel Selected { get; private set; }
+
+        #endregion
+
+        #region Commands
+
+        public DelegatingCommand ChooseElementCommand
+        {
+            get
+            {
+                if (_chooseElementCommand == null)
+                {
+                    _chooseElementCommand = new DelegatingCommand(
+                        param => DoChooseElement(),
+                        param => CanChooseElement());
+                }
+                return _chooseElementCommand;
+            }
+        }
+
+        #endregion
+
+        #region Messages
+
+        /// <summary>
+        /// A message that is sent out when an element has been chosen;
+        /// the message content is the element's view model with the element
+        /// wrapped inside.
+        /// </summary>
+        public Message<ViewModelMessageContent> ElementChosenMessage
+        {
+            get
+            {
+                if (_elementChosenMessage == null)
+                {
+                    _elementChosenMessage = new Message<ViewModelMessageContent>();
+                }
+                return _elementChosenMessage;
+            }
+        }
 
         #endregion
 
         #region Constructors
 
-        public ElementPickerViewModel(SettingsViewModel caller, bool allowControlElements)
+        public ElementPickerViewModel(bool allowControlElements)
         {
-            _caller = caller;
-            AvailableElements = new List<CategoryViewModel>();
+            Categories = new List<CategoryViewModel>();
             if (allowControlElements)
             {
-                AvailableElements.Add(
+                Categories.Add(
                     new CategoryViewModel(
                         "Kontroll-Elemente",
                         new Collection<ViewModelBase>()
@@ -62,7 +108,7 @@ namespace zaaReloaded2.ViewModels
                     )
                 );
             }
-            AvailableElements.Add(
+            Categories.Add(
                 new CategoryViewModel(
                     "Ausgabe-Elemente",
                     new Collection<ViewModelBase>()
@@ -87,6 +133,7 @@ namespace zaaReloaded2.ViewModels
         {
             ControlElementViewModel vm = new ControlElementViewModel(element);
             vm.DisplayString = element.Label;
+            vm.PropertyChanged += ElementViewModel_PropertyChanged;
             return vm;
         }
 
@@ -102,6 +149,31 @@ namespace zaaReloaded2.ViewModels
             return vm;
         }
 
+        void ElementViewModel_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
+        {
+            if (e.PropertyName == "IsSelected")
+            {
+                // Casting sender as ElementViewModel may result in Null, but this
+                // is a desired effect because category headings may be selected
+                // in a view, but are not valid ElementViewModels that we could
+                // 'choose'.
+                Selected = sender as ElementViewModel;
+            }
+        }
+
+        void DoChooseElement()
+        {
+            if (CanChooseElement())
+            {
+                ElementChosenMessage.Send(new ViewModelMessageContent(Selected));
+            }
+        }
+
+        bool CanChooseElement()
+        {
+            return Selected != null;
+        }
+
         #endregion
 
         #region Implementation ov ViewModelBase
@@ -115,7 +187,8 @@ namespace zaaReloaded2.ViewModels
 
         #region Fields
 
-        SettingsViewModel _caller;
+        DelegatingCommand _chooseElementCommand;
+        Message<ViewModelMessageContent> _elementChosenMessage;
 
         #endregion
     }