refactored observable

MainView.dfm

@@ -2,8 +2,8 @@ object MainViewForm: TMainViewForm
   Left = 0
   Top = 0
   Caption = 'SimpleMVVMDemo'
-  ClientHeight = 289
-  ClientWidth = 561
+  ClientHeight = 373
+  ClientWidth = 601
   Color = clBtnFace
   Font.Charset = DEFAULT_CHARSET
   Font.Color = clWindowText
@@ -17,8 +17,8 @@ object MainViewForm: TMainViewForm
   object GroupBox1: TGroupBox
     Left = 8
     Top = 8
-    Width = 161
-    Height = 121
+    Width = 185
+    Height = 153
     Caption = 'Example 1'
     TabOrder = 0
     object lblFullName: TLabel
@@ -46,10 +46,10 @@ object MainViewForm: TMainViewForm
     end
   end
   object GroupBox2: TGroupBox
-    Left = 184
+    Left = 208
     Top = 8
-    Width = 169
-    Height = 169
+    Width = 185
+    Height = 153
     Caption = 'Example 2'
     TabOrder = 1
     object lblClickCount: TLabel
@@ -84,10 +84,10 @@ object MainViewForm: TMainViewForm
     end
   end
   object GroupBox3: TGroupBox
-    Left = 368
+    Left = 408
     Top = 8
     Width = 185
-    Height = 169
+    Height = 153
     Caption = 'Example 3'
     TabOrder = 2
     object lblPrice: TLabel
@@ -114,4 +114,20 @@ object MainViewForm: TMainViewForm
       TabOrder = 1
     end
   end
+  object GroupBox4: TGroupBox
+    Left = 8
+    Top = 176
+    Width = 185
+    Height = 161
+    Caption = 'Example 4'
+    TabOrder = 3
+    object cbAvailableCountries: TComboBox
+      Left = 16
+      Top = 24
+      Width = 145
+      Height = 21
+      Style = csDropDownList
+      TabOrder = 0
+    end
+  end
 end

MainView.pas

@@ -41,6 +41,12 @@   TMainViewForm = class(TForm)
     [Bind('Enabled', 'ChosenTicket')]
     btnClear: TButton;
 
+    GroupBox4: TGroupBox;
+    [Bind('Value', 'Country')]
+    [BindOptions('AvailableCountries')]
+    [BindOptionsCaption('Choose...')]
+    cbAvailableCountries: TComboBox;
+
     procedure FormCreate(Sender: TObject);
   end;
 

MainViewModel.pas

@@ -27,6 +27,8 @@   TViewModel = class(TComponent)
     fHasClickedTooManyTimes: IObservable<Boolean>;
     fChosenTicket: IObservable<TTicket>;
     fTickets: TList<TTicket>;
+    fAvailableCountries: TArray<string>;
+    fCountry: IObservable<string>;
 
     function GetLastName: string;
     procedure SetLastName(const value: string);
@@ -48,6 +50,9 @@   TViewModel = class(TComponent)
 
     property ChosenTicket: IObservable<TTicket> read fChosenTicket;
     property Tickets: TList<TTicket> read fTickets;
+
+    property AvailableCountries: TArray<string> read fAvailableCountries;
+    property Country: IObservable<string> read fCountry;
   end;
 
 implementation
@@ -76,20 +81,24 @@ constructor TViewModel.Create(const firstName, lastName: string);
     end);
 
   // Example 2
-  fNumberOfClicks := TObservable<Integer>.Create(0);
+  fNumberOfClicks := TObservable<Integer>.Create;
   fHasClickedTooManyTimes := TDependentObservable<Boolean>.Create(
     function: Boolean
     begin
       Result := fNumberOfClicks.Value >= 3;
     end);
 
   // Example 3
-  fChosenTicket := TObservable<TTicket>.Create(nil);
-  fTickets := TObjectList<TTicket>.Create();
+  fChosenTicket := TObservable<TTicket>.Create;
+  fTickets := TObjectList<TTicket>.Create;
   fTickets.AddRange([
     TTicket.Create('Economy', 199.95),
     TTicket.Create('Business', 449.22),
     TTicket.Create('First Class', 1199.99)]);
+
+  // Example 4
+  fAvailableCountries := TArray<string>.Create('AU', 'NZ', 'US');
+  fCountry := TObservable<string>.Create;
 end;
 
 destructor TViewModel.Destroy;

SimpleMVVM.Binding.Components.pas

@@ -136,7 +136,7 @@ constructor TBinding<T>.Create(const component: T; const observable: IObservable
 begin
   inherited Create(component);
   fComponent := component;
-  fObservable := TDependentObservable<TValue>.Create(
+  fObservable := TDependentObservable.Create(
     Initialize(observable),
     procedure(const value: TValue)
     begin
@@ -246,11 +246,19 @@ function TEditBinding.Initialize(const observable: IObservable): TFunc<TValue>;
 {$REGION 'TComboBoxBinding'}
 
 procedure TComboBoxBinding.HandleChange(Sender: TObject);
+var
+  o: TObject;
 begin
   if fComponent.ItemIndex = -1 then
     fObservable.Value := nil
   else
-    fObservable.Value := fComponent.Items.Objects[fComponent.ItemIndex];
+  begin
+    o := fComponent.Items.Objects[fComponent.ItemIndex];
+    if o = nil then
+      fObservable.Value := fComponent.Items[fComponent.ItemIndex]
+    else
+      fObservable.Value := o;
+  end;
 end;
 
 procedure TComboBoxBinding.InitComponent;
@@ -262,8 +270,14 @@ function TComboBoxBinding.Initialize(const observable: IObservable): TFunc<TValu
 begin
   Result :=
     function: TValue
+    var
+      value: TValue;
     begin
-      fComponent.ItemIndex := fComponent.Items.IndexOfObject(observable.Value.AsObject);
+      value := observable.Value;
+      if value.IsObject then
+        fComponent.ItemIndex := fComponent.Items.IndexOfObject(value.AsObject)
+      else
+        fComponent.ItemIndex := fComponent.Items.IndexOf(value.ToString);
     end;
 end;