Introduction

The Visual Component Library supports another technique of file processing. Instead of saving the components as "streamable" objects, it gives you the option of saving the contents of controls. These contents are taken as data and not as VCL components. We will refer to this technique as file buffering.

To process the contents of controls as "streamable" values, the value of each object of the application is taken in its C/C++ context, as a variable created from known data types. The application itself is created like any other.

1. To start a new project, on the main menu, click File -> New -> VCL Forms Application - C++Builder
2. Change the Caption of the form to Clarksville Ice Cream
3. Complete the design of the form as follows:
    
   

   Control Name Caption Additional Properties TLabel   O&rder Date:   TEdit edtOrderDate     TLabel   Order Ti&me:   TEdit edtOrderTime     TLabel   &Flavor:   TEdit edtFlavor     TLabel   C&ontainer:   TEdit edtContainer     TLabel   &Ingredient:   TEdit edtIngredient     TLabel   &Scoops:   TEdit edtScoops   Alignment: taRightJustify NumbersOnly: True Text: 0.00 TLabel   Or&der Total:   TEdit edtTotalOrder   Alignment: taRightJustify Text: 0.00

4. Click the Scoops edit control
5. In the Object Inspector, click Events
6. Double-click OnExit
7. Implement the event as follows:

   //---------------------------------------------------------------------------
   void __fastcall TfrmMain::ledScoopsExit(TObject *Sender)
   {
       double priceContainer = 0.00,
   	   priceIngredient = 0.00,
   	   priceScoops = 0.00,
   	   orderTotal = 0.00;
       int numberOfScoops = 1;
   
       // Find out what container the customer requested
       // The price of a container depends on which one the customer selected
       if (ledContainer->Text == "Cone")
   	priceContainer = 0.55;
       else if (ledContainer->Text == "Cup")
   	priceContainer = 0.75;
       else
   	priceContainer = 1.15;
   
       // If the customer selected an ingredient, which is not "None", add $.95
       if (ledIngredient->Text != "None")
   	priceIngredient = 0.95;
   
       // Get the number of scoops
       numberOfScoops = StrToFloat(ledScoops->Text);
   
       if (numberOfScoops == 2)
   	priceScoops = 2.55;
       else if (numberOfScoops == 3)
   	priceScoops = 3.25;
       else
   	priceScoops = 1.85;
   
       // Make sure the user selected a flavor,
       // otherwise, there is no reason to process an order
       if (ledFlavor->Text != "")
   	orderTotal = priceScoops + priceContainer + priceIngredient;
   
       ledOrderTotal->Text = FormatFloat("0.00", orderTotal);
   }
   //---------------------------------------------------------------------------

8. Press F12 to return to the form
9. In the Tool Palette, click Dialogs
10. Click TOpenDialog and click the form
11. In the Object Inspector, change its properties as follows:
    DefaultExt: cic
    Filter: Clarksville Ice Create File (*.cic)|*.cic|All Files (*.*)|*.*
    Name: dlgOpen
    Title: Open a Clarksville Ice Create Order
12. In the Dialogs section of the Tool Palette, click TSaveDialog and click the form
13. Using the Object Inspector, change its properties as follows:
    DefaultExt: cic
    Filter: Clarksville Ice Create File (*.cic)|*.cic|All Files (*.*)|*.*
    Name: dlgSave
    Title: Save the Current Clarksville Ice Create Order
14.  In the Standard section of the Tool Palette, click TMainMenu and click the form
15. In the Object Inspector, click Name and type mnuMain and press Enter
16. On the form, double-click mnuMain
17. Right-click the Menu Designer and click Insert From Templates...
18. In the list, click File Menu
19. Click OK
20. In the Menu Designer, double-click New
21. Implement the event as follows:

    //---------------------------------------------------------------------------
    void __fastcall TfrmMain::New1Click(TObject *Sender)
    {
        edtOrderDate->Text = FormatDateTime("mm/dd/yyyy", TDateTime::CurrentDate());
        edtOrderTime->Text = FormatDateTime("hh:nn ampm", TDateTime::CurrentTime());
        ledFlavor->Text = "Vanilla";
        ledContainer->Text = "Cone";
        ledIngredient->Text = "None";
    }
    //---------------------------------------------------------------------------

22. Press F12 to display the form
23. Double-click an unoccupied area of the form
24. Implement the event as follows:

    //---------------------------------------------------------------------------
    void __fastcall TfrmMain::FormCreate(TObject *Sender)
    {
        New1Click(Sender);
    }
    //---------------------------------------------------------------------------

To create a file, you can use the TFileStream class reviewed earlier, using the same rules. To write data to a file, you can call the TFileStream::WriteBuffer() method. Its syntax is:

void __fastcall WriteBuffer(const void *Buffer, int Count);

The WriteBuffer() method is used when you must let the compiler know the amount of memory space you want to use for a particular variable. It requires two arguments. The first, Buffer, is the value that needs to be saved. The Count parameter specifies the number of bytes that the value will need to the stored.

1. In the Menu Designer, double-click Save
2. Implement the event as follows:

   //---------------------------------------------------------------------------
   void __fastcall TfrmMain::Save1Click(TObject *Sender)
   {
   	TFileStream *fsIceCreamer;
   
   	wchar_t orderDate[40];
   	wchar_t orderTime[40];
   	wchar_t flavor[40];
   	wchar_t container[40];
   	wchar_t ingredient[40];
   	wchar_t scoops[20];
   	wchar_t orderTotal[20];
   
   	if( dlgSave->Execute() )
   	{
   	    try {
   		StrCopy(orderDate, edtOrderDate->Text.c_str());
   		StrCopy(orderTime, edtOrderTime->Text.c_str());
   		StrCopy(flavor, ledFlavor->Text.c_str());
   		StrCopy(container, ledContainer->Text.c_str());
   		StrCopy(ingredient, ledIngredient->Text.c_str());
   		StrCopy(scoops, ledScoops->Text.c_str());
   		StrCopy(orderTotal, ledOrderTotal->Text.c_str());
   
   		fsIceCreamer = new TFileStream(dlgSave->FileName, fmCreate);
   
   		fsIceCreamer->WriteBuffer(&orderDate, 40);
   		fsIceCreamer->WriteBuffer(&orderTime, 40);
   		fsIceCreamer->WriteBuffer(&flavor, 40);
   		fsIceCreamer->WriteBuffer(&container, 40);
   		fsIceCreamer->WriteBuffer(&ingredient, 40);
   		fsIceCreamer->WriteBuffer(&scoops, 20);
   		fsIceCreamer->WriteBuffer(&orderTotal, 20);
   
   		New1Click(Sender);
   	    }
   	    __finally
   	    {
   		delete fsIceCreamer;
   	    }
   	}
   }
   //---------------------------------------------------------------------------

3. To execute, press F9
4. Enter some values as follows:
    
   
   
5. Clisk Save
6. Set the file name to 1001
7. Click Save
8. Enter some values as follows:
    
   
9. Click Save
10. Set the file name to 1002 and click Save

Data reading in this context is performed using the ReadBuffer() method of the TFileStream class. Its syntax is:

void __fastcall ReadBuffer(void *Buffer, int Count);

The ReadBuffer() method also requires two pieces of information. The Buffer parameter is the value that needs to be read. The Count parameter is used to specify the number of bytes that need to be read for the Buffer value.

1. In the Menu Designer, double-click Open...
2. Implement the event as follows:

   //---------------------------------------------------------------------------
   void __fastcall TfrmMain::Open1Click(TObject *Sender)
   {
       TFileStream *fsIceCream;
       wchar_t orderDate[40];
       wchar_t orderTime[40];
       wchar_t flavor[40];
       wchar_t container[40];
       wchar_t ingredient[40];
       wchar_t scoops[20];
       wchar_t orderTotal[20];
   
       if( dlgOpen->Execute() )
       {
   	try {
   		fsIceCream = new TFileStream(dlgOpen->FileName, fmOpenRead);
   
   		fsIceCream->ReadBuffer(&orderDate, 40);
   		fsIceCream->ReadBuffer(&orderTime, 40);
   		fsIceCream->ReadBuffer(&flavor, 40);
   		fsIceCream->ReadBuffer(&container, 40);
   		fsIceCream->ReadBuffer(&ingredient, 40);
   		fsIceCream->ReadBuffer(&scoops, 20);
   		fsIceCream->ReadBuffer(&orderTotal, 20);
   
   		edtOrderDate->Text = orderDate;
   		edtOrderTime->Text = orderTime;
   		ledFlavor->Text = flavor;
   		ledContainer->Text = container;
   		ledIngredient->Text = ingredient;
   		ledScoops->Text = scoops;
   		ledOrderTotal->Text = orderTotal;
   	}
   	__finally
   	{
   		delete fsIceCream;
   	}
       }
   }
   //---------------------------------------------------------------------------

3. On the Menu Designer, double-click Exit
4. Close the Menu Designer
5. Implement the event as follows:

   //---------------------------------------------------------------------------
   void __fastcall TfrmMain::Exit1Click(TObject *Sender)
   {
       this->Close();
   }
   //---------------------------------------------------------------------------

6. To execute, on the main menu, click Run -> Run
7. Using the main menu, open one of the previously saved file