Add OneWaySeqT

src/Elmish.WPF/Binding.fs

@@ -125,6 +125,22 @@ module Binding =
     let id<'a> : string -> Binding<'a, 'a, 'a> =
       TwoWay.id
       |> createBindingT
+
+  /// <summary>
+  ///   The strongly-typed counterpart of <c>Binding.oneWaySeq</c> with parameter <c>getId</c>.
+  ///   Exposes an <c>ObservableCollection</c> of child items for binding.
+  ///   Allows a more efficient update than would be possible without using ids.
+  /// </summary>
+  module OneWaySeqT =
+
+    /// <summary>
+    /// Elemental instance of a OneWaySeqT binding
+    /// </summary>
+    /// <param name="itemEquals">Defines whether an item is "equal" and needs to be updated if the ids are the same</param>
+    /// <param name="getId">Unique identifier for each item in the list (for efficient updates).</param>
+    let id itemEquals (getId: 'a -> 'id) : string -> Binding<_, 'msg, _> =
+      OneWaySeq.create itemEquals getId
+      |> createBindingT
 
   /// <summary>
   ///   Strongly-typed bindings that dispatch messages from the view.

src/Samples/SubModelStatic.Core/Program.fs

@@ -11,7 +11,8 @@ module Counter =
 
   type Model =
     { Count: int
-      StepSize: int }
+      StepSize: int
+      History: (int * int) list }
 
   type Msg =
     | Increment
@@ -21,14 +22,15 @@ module Counter =
 
   let init =
     { Count = 0
-      StepSize = 1 }
+      StepSize = 1
+      History = [] }
 
   let canReset = (<>) init
 
   let update msg m =
     match msg with
-    | Increment -> { m with Count = m.Count + m.StepSize }
-    | Decrement -> { m with Count = m.Count - m.StepSize }
+    | Increment -> { m with Count = m.Count + m.StepSize; History = (m.Count, m.History.Length) :: m.History }
+    | Decrement -> { m with Count = m.Count - m.StepSize; History = (m.Count, m.History.Length) :: m.History }
     | SetStepSize x -> { m with StepSize = x }
     | Reset -> init
 
@@ -41,7 +43,7 @@ type [<AllowNullLiteral>] CounterViewModel (args) =
     >> Binding.mapModel (fun (m: Counter.Model) -> m.StepSize)
     >> Binding.mapMsg Counter.Msg.SetStepSize
 
-  new() = CounterViewModel(Counter.init |> ViewModelArgs.simple)
+  new() = CounterViewModel({ Counter.init with History = [ (3,1); (0,0) ] } |> ViewModelArgs.simple)
 
   member _.StepSize
     with get() = base.Get() stepSizeBinding
@@ -50,6 +52,7 @@ type [<AllowNullLiteral>] CounterViewModel (args) =
   member _.Increment = base.Get() (Binding.CmdT.setAlways Counter.Increment)
   member _.Decrement = base.Get() (Binding.CmdT.setAlways Counter.Decrement)
   member _.Reset = base.Get() (Binding.CmdT.set Counter.canReset Counter.Reset)
+  member _.History = base.Get() (Binding.OneWaySeqT.id (=) snd >> Binding.mapModel (fun m -> m.History))
 
 
 module Clock =

src/Samples/SubModelStatic/Counter.xaml

@@ -6,12 +6,37 @@
              xmlns:vm="clr-namespace:Elmish.WPF.Samples.SubModelStatic;assembly=SubModelStatic.Core"
              mc:Ignorable="d"
              d:DataContext="{d:DesignInstance Type=vm:CounterViewModel, IsDesignTimeCreatable=True}">
-  <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Top">
-    <TextBlock Text="{Binding CounterValue, StringFormat='Counter value: {0}'}" Width="110" Margin="0,5,10,5" />
-    <Button Command="{Binding Decrement}" Content="-" Margin="0,5,10,5" Width="30" />
-    <Button Command="{Binding Increment}" Content="+" Margin="0,5,10,5" Width="30" />
-    <TextBlock Text="{Binding StepSize, StringFormat='Step size: {0}'}" Width="70" Margin="0,5,10,5" />
-    <Slider Value="{Binding StepSize}" TickFrequency="1" Maximum="10" Minimum="1" IsSnapToTickEnabled="True" Width="100" Margin="0,5,10,5" />
-    <Button Command="{Binding Reset}" Content="Reset" Margin="0,5,10,5" Width="50" />
-  </StackPanel>
+  <Grid>
+    <Grid.RowDefinitions>
+      <RowDefinition/>
+      <RowDefinition/>
+    </Grid.RowDefinitions>
+    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Top">
+      <TextBlock Text="{Binding CounterValue, StringFormat='Counter value: {0}'}" Width="110" Margin="0,5,10,5" />
+      <Button Command="{Binding Decrement}" Content="-" Margin="0,5,10,5" Width="30" />
+      <Button Command="{Binding Increment}" Content="+" Margin="0,5,10,5" Width="30" />
+      <TextBlock Text="{Binding StepSize, StringFormat='Step size: {0}'}" Width="70" Margin="0,5,10,5" />
+      <Slider Value="{Binding StepSize}" TickFrequency="1" Maximum="10" Minimum="1" IsSnapToTickEnabled="True" Width="100" Margin="0,5,10,5" />
+      <Button Command="{Binding Reset}" Content="Reset" Margin="0,5,10,5" Width="50" />
+    </StackPanel>
+    <DockPanel Grid.Row="1" HorizontalAlignment="Stretch" VerticalAlignment="Top">
+      <TextBlock DockPanel.Dock="Left" Margin="0,5,10,5">History:</TextBlock>
+      <TextBlock Margin="2,5,2,5">
+        <Run Text="{Binding CounterValue, Mode=OneWay, StringFormat='({0},'}" />
+        <Run Text="{Binding History.Count, Mode=OneWay, StringFormat='{}{0})'}" />
+      </TextBlock>
+      <ItemsControl ItemsSource="{Binding History}">
+        <ItemsControl.ItemTemplate>
+          <DataTemplate>
+            <TextBlock Text="{Binding}" TextDecorations="Strikethrough" Margin="2,5,2,5" />
+          </DataTemplate>
+        </ItemsControl.ItemTemplate>
+        <ItemsControl.ItemsPanel>
+          <ItemsPanelTemplate>
+            <StackPanel Orientation="Horizontal"/>
+          </ItemsPanelTemplate>
+        </ItemsControl.ItemsPanel>
+      </ItemsControl>
+    </DockPanel>
+  </Grid>
 </UserControl>

src/Samples/SubModelStatic/MainWindow.xaml

@@ -6,7 +6,7 @@
         xmlns:local="clr-namespace:Elmish.WPF.Samples.SubModelStatic"
         xmlns:vm="clr-namespace:Elmish.WPF.Samples.SubModelStatic;assembly=SubModelStatic.Core"
         Title="Sub-model"
-        Height="270"
+        Height="300"
         Width="500"
         WindowStartupLocation="CenterScreen"
         mc:Ignorable="d"