Component Writer's Guide Supplement

PAGE 4-10
Remove:
typedef TFloatProperty ThisClass;


PAGE 4-13
The snippet that called RegisterPropertyEditor
incorrectly passes type names as parameters.
When specifying types as parameters in calls
to RegisterPropertyEditor use __classid(TypeName).
So your own call should like:

   RegisterPropertyEditor(__typeinfo(TMenuItem),__classid(TMenu),
   "",__classid(TMenuItemProperty));


PAGE 8-4
When defining and declaring Message handlers for user messages
and Windows messages use a TMessage reference for the single
parameter rather than a TMessage pointer.

Change:
void __fastcall WMPaint(TWMPaint* Message)

To:
void __fastcall WMPaint(TWMPaint& Message)


PAGE 8-7
Change:
void __fastcall CMChangeColor(TMessage* Message);

To:
void __fastcall CMChangeColor(TMessage& Message);

Change:
void __fastcall TMyControl::CMChangeColor(TMessage* Message);

To:
void __fastcall TMyControl::CMChangeColor(TMessage& Message);


PAGE 12-4
Change:
void __fastcall WMSize(TWMSize* Message);

To:
void __fastcall WMSize(TWMSize& Message);

Change:
 
void __fastcall TSampleCalendar::WMSize(TMessage* Message);

To:
void __fastcall TSampleCalendar::WMSize(TMessage& Message);

Change:
DefaultColWidth = (Message->Width - GridLines)/7;
DefaultRowHeight = (Message->Height - GridLines)/7;

To:
DefaultColWidth = (Message.Width - GridLines)/7;
DefaultRowHeight = (Message.Height - GridLines)/7;


PAGE 14-2
In the public: section of TAboutBoxDlg,
the constructor is missing, it should read:

class TAboutDlgBox : public TComponent
{
private:
protected:
public:
virtual __fastcall TAboutDlgBox(TComponent* Owner);
__published:
};


PAGE 14-3 
In the public: section of TAboutBoxDlg,
the constructor is missing, it should read:

//---------------------------------------------------------------
#include 
#pragma hdrstop
#include "aboutdlg.h"

//---------------------------------------------------------------
__fastcall TAboutDlgBox::TAboutDlgBox(TComponent* Owner)
           : TComponent(Owner)
{
}
//---------------------------------------------------------------

//---------------------------------------------------------------
namespace Aboutdlg
{
   void __fastcall Register()
      {
      TComponentClass classes[1] ={__classid(TAboutDlgBox)};
      RegisterComponents("Samples", classes,0);
      }
}
//---------------------------------------------------------------



PAGE 14-6 
The final return from TAboutBoxDlg::Execute()                                                            
uses return Result==IDOK, it should read:

bool __fastcall TAboutDlgBox::Execute()
{
   AboutBox=new TAboutBox(Application);
   bool Result;
   try {
       if (ProductName=="";)
          ProductName=Application->Title;
          AboutBox->ProductName->Caption=ProductName;
          AboutBox->Version->Caption=Version;
          AboutBox->Copyright->Caption=Copyright;
          AboutBox->Comments->Caption=Comments;
          AboutBox->Caption="About "+ProductName;
          Result=(AboutBox->ShowModal() == IDOK);
          }
       catch(...)
          {
          Result=false;
          }
   AboutBox->Free();
   return Result;
}