ComponentToString (C++)

Description

This example shows how to use the built-in component streaming support to convert any component into a string and convert that string back into a component.

Code

#include <memory>       //For STL auto_ptr class

class MyScrollBar : public TScrollBar
{
__published:	// IDE-managed Components
private:	// User declarations
public:		// User declarations
	__fastcall MyScrollBar(TComponent* Owner);
};

__fastcall MyScrollBar::MyScrollBar(TComponent* Owner)
	: TScrollBar(Owner)
{
}

void RegisterClassesWithStreamingSystem(void)
{
  // Make sure that, as part of the startup
  // code, the streaming classes are registered
  // with the streaming system.

  #pragma startup RegisterClassesWithStreamingSystem

  Classes::RegisterClass(__classid(MyScrollBar));
}

MyScrollBar *ScrollBar1;

String __fastcall ComponentToString(TComponent *c)
{
  String as;
  std::auto_ptr<TMemoryStream> pms(new TMemoryStream);
  std::auto_ptr<TStringStream> pss(new TStringStream(as));

  try
  {
	pms->WriteComponent(c);
	pms->Seek(0, soFromBeginning);
	ObjectBinaryToText(pms.get(), pss.get());
    pss->Seek(0, soFromBeginning);
    as = pss->DataString;
  }
  catch(...)
  {
    ShowMessage("Streaming error.");
  }

  return as;
}

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  Memo1->Text = ComponentToString(ScrollBar1);
}

TComponent *__fastcall StringToComponent(String as)

{
  std::auto_ptr<TMemoryStream> pms(new TMemoryStream);
  std::auto_ptr<TStringStream> pss(new TStringStream(as));
  TComponent *pc;

  try
  {
	ObjectTextToBinary(pss.get(), pms.get());
    pms->Seek(0, soFromBeginning);
  }
  catch(...)
  {
    ShowMessage("Streaming error.");
  }

  pc = pms->ReadComponent(NULL);
  return pc;
}

void __fastcall TForm1::Button2Click(TObject *Sender)
{
  TComponent *temp = StringToComponent(Memo1->Text);
  ScrollBar1->Free();

  ScrollBar1 = dynamic_cast<MyScrollBar *>(temp);
  ScrollBar1->Parent = Form1;
  ScrollBar1->Visible = TRUE;
}

__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
  ScrollBar1 = new MyScrollBar(Form1);  // Form1 will clean up the scroll bar.
  ScrollBar1->Parent = Form1;
  ScrollBar1->Visible = TRUE;
  ScrollBar1->Top = 48;
  ScrollBar1->Left = 250;
  ScrollBar1->Name = "Ricksbar";
}

Uses

• System.Classes.TStream.ReadComponent ( fr | de | ja )
• System.Classes.TStream.WriteComponent ( fr | de | ja )
• System.Classes.TStringStream.DataString ( fr | de | ja )
• System.Classes.ObjectBinaryToText ( fr | de | ja )
• System.Classes.ObjectTextToBinary ( fr | de | ja )
• System.Classes.TCustomMemoryStream.Seek ( fr | de | ja )
• System.Classes.TStringStream.Create ( fr | de | ja )
• System.Classes.TMemoryStream ( fr | de | ja )
• System.Classes.TStringStream ( fr | de | ja )
• System.Classes.TStream ( fr | de | ja )
• System.Classes.RegisterClass ( fr | de | ja )