FireMonkey C++ on iOS: Create/Open File Exception

I want to create/read a generic file by FireMonkey C++ in iOS. I've a problem (exception) in file action.

my sample code is :

#include

#pragma hdrstop

#include "Unit1.h"

//---------------------------------------------------------------------------

#pragma package(smart_init)

#pragma resource "*.fmx"

TForm1 *Form1;

//---------------------------------------------------------------------------

__fastcall TForm1::TForm1(TComponent* Owner)

: TForm(Owner)

{

}

//---------------------------------------------------------------------------

void __fastcall TForm1::CreateFileClick(TObject *Sender)

{

MessageDlg(L"Start ...", TMsgDlgType::mtError, TMsgDlgButtons() << TMsgDlgBtn::mbYes, 0);

    TFileStream *writeFS = NULL;

    try

    {

        writeFS = new TFileStream(L"sample.txt", fmCreate | fmShareDenyNone);

        writeFS->WriteComponent(Edit1);

MessageDlg(L"create finished ...", TMsgDlgType::mtInformation, TMsgDlgButtons() << TMsgDlgBtn::mbYes, 0);

    }

    catch(...)

    {

        if (writeFS != NULL)

    delete writeFS;

MessageDlg(L"create failed!", TMsgDlgType::mtError, TMsgDlgButtons() << TMsgDlgBtn::mbYes, 0);

    }

}

//---------------------------------------------------------------------------

void __fastcall TForm1::ReadFileClick(TObject *Sender)

{

    Edit2->Text = L"";

    TFileStream *readFS = NULL;

    try

    {

        readFS = new TFileStream(L"sample.txt", fmOpenRead);

        readFS->ReadComponent(Edit2);

MessageDlg(L"read finished ...\n" + Edit2->Text, TMsgDlgType::mtInformation, TMsgDlgButtons() << TMsgDlgBtn::mbYes, 0);

    }

    catch(...)

    {

        if (readFS != NULL)

    delete readFS;

MessageDlg(L"read failed!", TMsgDlgType::mtError, TMsgDlgButtons() << TMsgDlgBtn::mbYes, 0);

    }

}

//---------------------------------------------------------------------------

but in run-time, iPhone device raise an exception below:

Project Project1 raised exception class EFCreateError with message 'Cannot create file "/sample.txt". Not a directory'.

could you help me.

regards 

Ghader