From d734b0666a6822d59a4d21e4a05fefec1a2081d7 Mon Sep 17 00:00:00 2001
From: Ionite <dev@ionite.io>
Date: Tue, 21 Nov 2023 15:25:24 -0500
Subject: [PATCH] Add ViewModelBase.ViewModelState and OnInitialLoaded virtual
 method

---
 .../Models/ViewModelState.cs                  | 15 ++++++
 .../ViewModels/Base/ViewModelBase.cs          | 53 +++++++++++++++----
 2 files changed, 57 insertions(+), 11 deletions(-)
 create mode 100644 StabilityMatrix.Avalonia/Models/ViewModelState.cs

diff --git a/StabilityMatrix.Avalonia/Models/ViewModelState.cs b/StabilityMatrix.Avalonia/Models/ViewModelState.cs
new file mode 100644
index 00000000..d195a7a6
--- /dev/null
+++ b/StabilityMatrix.Avalonia/Models/ViewModelState.cs
@@ -0,0 +1,15 @@
+using System;
+
+namespace StabilityMatrix.Avalonia.Models;
+
+/// <summary>
+///
+/// </summary>
+[Flags]
+public enum ViewModelState : uint
+{
+    /// <summary>
+    /// View Model has been initially loaded
+    /// </summary>
+    InitialLoaded = 1 << 0,
+}
diff --git a/StabilityMatrix.Avalonia/ViewModels/Base/ViewModelBase.cs b/StabilityMatrix.Avalonia/ViewModels/Base/ViewModelBase.cs
index 0cce47ba..0d9899cc 100644
--- a/StabilityMatrix.Avalonia/ViewModels/Base/ViewModelBase.cs
+++ b/StabilityMatrix.Avalonia/ViewModels/Base/ViewModelBase.cs
@@ -2,14 +2,18 @@
 using System.Threading.Tasks;
 using AsyncAwaitBestPractices;
 using CommunityToolkit.Mvvm.ComponentModel;
+using JetBrains.Annotations;
 using StabilityMatrix.Avalonia.Models;
 
 namespace StabilityMatrix.Avalonia.ViewModels.Base;
 
 public class ViewModelBase : ObservableValidator, IRemovableListItem
 {
+    [PublicAPI]
+    protected ViewModelState ViewModelState { get; private set; }
+
     private WeakEventManager? parentListRemoveRequestedEventManager;
-    
+
     public event EventHandler ParentListRemoveRequested
     {
         add
@@ -20,24 +24,51 @@ public class ViewModelBase : ObservableValidator, IRemovableListItem
         remove => parentListRemoveRequestedEventManager?.RemoveEventHandler(value);
     }
 
-    protected void RemoveFromParentList() => parentListRemoveRequestedEventManager?.RaiseEvent(
-        this, EventArgs.Empty, nameof(ParentListRemoveRequested));
-    
+    protected void RemoveFromParentList() =>
+        parentListRemoveRequestedEventManager?.RaiseEvent(
+            this,
+            EventArgs.Empty,
+            nameof(ParentListRemoveRequested)
+        );
+
+    /// <summary>
+    /// Called when the view's LoadedEvent is fired.
+    /// </summary>
     public virtual void OnLoaded()
     {
-        
+        if (!ViewModelState.HasFlag(ViewModelState.InitialLoaded))
+        {
+            ViewModelState |= ViewModelState.InitialLoaded;
+            OnInitialLoaded();
+        }
     }
 
+    /// <summary>
+    /// Called the first time the view's LoadedEvent is fired.
+    /// Sets the <see cref="ViewModelState.InitialLoaded"/> flag.
+    /// </summary>
+    protected virtual void OnInitialLoaded() { }
+
+    /// <summary>
+    /// Called asynchronously when the view's LoadedEvent is fired.
+    /// Runs on the UI thread via Dispatcher.UIThread.InvokeAsync.
+    /// The view loading will not wait for this to complete.
+    /// </summary>
     public virtual Task OnLoadedAsync()
     {
         return Task.CompletedTask;
     }
-    
-    public virtual void OnUnloaded()
-    {
-        
-    }
-    
+
+    /// <summary>
+    /// Called when the view's UnloadedEvent is fired.
+    /// </summary>
+    public virtual void OnUnloaded() { }
+
+    /// <summary>
+    /// Called asynchronously when the view's UnloadedEvent is fired.
+    /// Runs on the UI thread via Dispatcher.UIThread.InvokeAsync.
+    /// The view loading will not wait for this to complete.
+    /// </summary>
     public virtual Task OnUnloadedAsync()
     {
         return Task.CompletedTask;