XE5: Probleme mit LiveBindings "CheckedState(Self)"

[Sir Rufo]

Zitat von Kralle:

Was mache ich falsch?

Du benutzt Livebindings

Dafür nehme ich MVVM, das kann ich immer so hinbiegen wie ich möchte und bin nicht darauf angewiesen, ob Komponente X und Eigenschaft Y auch für Livebindings vorgesehen vorbereitet ist.

Delphi-Quellcode:

unit ViewFormMain;

interface

  uses
    Windows,
    Messages,
    SysUtils,
    Variants,
    Classes,
    Graphics,
    Controls,
    Forms,
    Dialogs,
    StdCtrls;

  type
    TViewModel = class
    private
      FValue    : Boolean;
      FOnUpdate : TNotifyEvent;
      procedure SetValue( const Value : Boolean );
    protected
      procedure DoUpdate;
    public
      property OnUpdate : TNotifyEvent read FOnUpdate write FOnUpdate;
      property Value    : Boolean read FValue write SetValue;
    end;

    TMainFormView = class( TForm )
      Edit1 : TEdit;         // OI: OnChange => ControlChange
      Edit2 : TEdit;         // OI: OnChange => ControlChange
      Edit3 : TEdit;         // OI: OnChange => ControlChange
      CheckBox1 : TCheckBox; // OI: OnClick => ControlChange
      procedure ControlChange( Sender : TObject );
      procedure FormShow( Sender : TObject );
    private
      FModelLoading : Boolean;
      FViewModel    : TViewModel;
    protected
      procedure DoLoadFromModel; virtual;
      procedure DoSaveToModel; virtual;
      procedure ViewModelUpdate( Sender : TObject );
    protected
      procedure LoadFromModel;
      procedure SaveToModel;
      procedure SyncWithModel;
    public
      procedure AfterConstruction; override;
      procedure BeforeDestruction; override;
      property ViewModel : TViewModel read FViewModel;
    end;

  var
    MainFormView : TMainFormView;

implementation

{$R *.dfm}
  { TForm1 }

  procedure TMainFormView.AfterConstruction;
    begin
      inherited;
      FViewModel          := TViewModel.Create;
      FViewModel.OnUpdate := ViewModelUpdate;
    end;

  procedure TMainFormView.BeforeDestruction;
    begin
      inherited;
      FViewModel.Free;
    end;

  procedure TMainFormView.ControlChange( Sender : TObject );
    begin
      SyncWithModel;
    end;

  procedure TMainFormView.DoLoadFromModel;
    begin
      // Binding Model => View
      CheckBox1.Checked := ViewModel.Value;
      Edit1.Enabled     := not ViewModel.Value;
      Edit2.Enabled     := not ViewModel.Value;
      Edit3.Enabled     := not ViewModel.Value;
    end;

  procedure TMainFormView.DoSaveToModel;
    begin
      // Binding View => Model
      ViewModel.Value := CheckBox1.Checked;
    end;

  procedure TMainFormView.FormShow( Sender : TObject );
    begin
      LoadFromModel;
    end;

  procedure TMainFormView.LoadFromModel;
    begin
      if FModelLoading
      then
        Exit;

      FModelLoading := True;
      try
        DoLoadFromModel;
      finally
        FModelLoading := False;
      end;
    end;

  procedure TMainFormView.SaveToModel;
    begin
      if FModelLoading
      then
        Exit;

      DoSaveToModel;
    end;

  procedure TMainFormView.SyncWithModel;
    begin
      SaveToModel;
      LoadFromModel;
    end;

  procedure TMainFormView.ViewModelUpdate( Sender : TObject );
    begin
      LoadFromModel;
    end;

  { TViewModel }

  procedure TViewModel.DoUpdate;
    begin
      if Assigned( OnUpdate )
      then
        OnUpdate( Self );
    end;

  procedure TViewModel.SetValue( const Value : Boolean );
    begin
      if Value = FValue
      then
        Exit;

      FValue := Value;
      DoUpdate;
    end;

end.