Custom Component: Combobox Property

Comments

• Samuel Smith

  June 2019 edited June 2019

  Alright, I'll write down what I've come up with. There's no real easy way to do this, and you have to write a custom property editor.
  
  First, I made a custom property.
  

  class CustomStringList : public TStringList
  {
     typedef TStringList inherited;
    private:
    void __fastcall SetValue( UnicodeString Value )
      {
        [indent]SelectedItem = IndexOf( Value );[/indent]
       };
       UnicodeString __fastcall GEtStrValue()
      {
           if (SelectedItem >= 0 && SelectedItem < Count )
                   return Strings[SelectedItem];
            else
           return "";
      };
  public:
     int SelectedItem;
     __property UnicodeString SelectedString = {read=GetValue, write=SetValue};
     __fastcall CustomSTringList() : TStringList {SelectedItem = -1;};
  
  }
  

  
  Then I had to make a custom property editor

  class CustomStringListPropertyEditor : public TfrxPropertyEditor
  {
    typedef TfrxPropertyEditor inherited;
    public:
      TfrxPropertyAttributes virtual __fastcall GetAttributes()
      {
        TfrxPropertyAttributes Results;
        Results << paReadOnly;
        Results << paValueList;
        return Results;
      };
      
      virtual void __fastcall GetValues()
      {
          // Fetch all the current available options.
          CustomStringList* SL = (CustomStringList*) GetOrdValue(); // The pointer is stored in the int value
          Values->Clear();
          Values->AddStrings( SL );
      };
  
      inline __fastcall virtual CustomStringListPropertyEditor( TfrxCusotmDesigner* Designer); TfrxPropertyEditor(Designer) {};
  };
  

  
  In the custom component I needed to use that class as a property in the published section

  class CustomComponent : publicTfrxComponent
  {
     private:
        CustomStringList* SL;
    __published
        __property CustomStringList* Combobox = {read=SL, write=SL};
  };
  

  
  And then, in the initialization of the component, you have to register the property editor (as well as the custom component)

  ....
  (frxPropertyEditors())->Register( __delphirtti(CustomStringList), NULL, "", __classid(CustomStringListPropertyEditor));