Creating custom TSetProperty property editor

Question

I\'m trying to create a custom property editor for some custom component. The custom property editor is intended to edit some set property, like

type
  TButt         


        

Answer 1

Finally I got a solution... After testing everything I could imagine - without success - I started searching for something "new" in DesignEditors.pas and DesignIntf.pas units. Reading GetEditorClass() function, I discovered that it first checks for a PropertyMapper. A property mapper can be registered using RegisterPropertyMapper() function. Using it instead of RegisterPropertyEditor() works just as expected. Here is my modified, working code, also showing some interesting application for this: show or hide some options of my set-based property, based on some criteria:

unit Button1;

interface

uses
  System.SysUtils, System.Classes, Vcl.Controls, Vcl.StdCtrls,
  DesignIntf, DesignEditors;

type
  TButtonOption = (boOptionA, boOptionB, boOptionC);
  TButtonOptions = set of TButtonOption;

type
  TButtonEx = class(TButton)
  private
    FOptions: TButtonOptions;
    function GetOptions: TButtonOptions;
    procedure SetOptions(Value: TButtonOptions);
  published
    property Options: TButtonOptions read GetOptions write SetOptions default [];
  end;

  TMySetProperty = class(TSetProperty)
  private
    FProc: TGetPropProc;
    procedure InternalGetProperty(const Prop: IProperty);
  public
    procedure GetProperties(Proc: TGetPropProc); override;
  end;

procedure Register;

implementation

uses
  TypInfo;

// TButtonEx - sample component

function TButtonEx.GetOptions: TButtonOptions;
begin
  Result := FOptions;
end;

procedure TButtonEx.SetOptions(Value: TButtonOptions);
begin
  if FOptions <> Value then
  begin
    FOptions := Value;
  end;
end;

// Returns TMySetProperty as the property editor used for Options in TButtonEx class
function MyCustomPropMapper(Obj: TPersistent; PropInfo: PPropInfo): TPropertyEditorClass;
begin
  Result := nil;
  if Assigned(Obj) and (Obj is TButtonEx) and SameText(String(PropInfo.Name), 'Options') then begin
    Result := TMySetProperty;
  end;
end;

procedure Register;
begin
  RegisterComponents('Samples', [TButtonEx]);
  // RegisterPropertyEditor does not work for set-based properties.
  // We use RegisterPropertyMapper instead
  RegisterPropertyMapper(MyCustomPropMapper);
end;

procedure TMySetProperty.GetProperties(Proc: TGetPropProc);
begin
  // Save the original method received
  FProc := Proc;
  // Call inherited, but passing our internal method as parameter
  inherited GetProperties(InternalGetProperty);
end;

procedure TMySetProperty.InternalGetProperty(const Prop: IProperty);
var
  i: Integer;
begin
  if not Assigned(FProc) then begin   // just in case
    Exit;
  end;

  // Now the interesting stuff. I just want to show boOptionA and boOptionB in Object inspector
  // So I call the original Proc in those cases only
  // boOptionC still exists, but won't be visible in object inspector
  for i := 0 to PropCount - 1 do begin
    if SameText(Prop.GetName, 'boOptionA') or SameText(Prop.GetName, 'boOptionB') then begin
      FProc(Prop);       // call original method
    end;
  end;
end;

end.