C++ builder (no idea what to do with this code) - c++builder

Question

Sorry if this is wrong place to ask. I have 2 pieces of code given to me:
IdHTTP1->Head("http://dsrt.dyndns.org/files/MAIN.zip");
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->Date));
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->Expires));
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->LastModified));
and also this:
TDateTime dt;
AnsiString str = DateToStr(dt);
IdHTTP1->Head("http://dsrt.dyndns.org/files/MAIN.zip");
if(DateToStr(IdHTTP1->Response->Date) != str)
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->Date));
if(DateToStr(IdHTTP1->Response->Expires) != str)
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->Expires));
if(DateToStr(IdHTTP1->Response->LastModified) != str)
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->LastModified));
Somehow it's supposed to return a date when file was uploaded. But I have no clue how to get c++ builder to compile it. I get syntax errors and "multiple memo1 something" error. Please help.

Answer 1

TMemo is an Embarcadero visual UI component. TIdHTTP is a component of the Indy Project, which ships preinstalled in Delphi and C++Builder.
The code you were given is UI-related code, so create UI for it. In the C++Builder IDE, create a new TForm class, drop a TMemo on it and name it Memo1, and drop a TIdHTTP component and name it IdHTTP1, and then use something like a button OnClick handler to invoke the HTTP code, eg:
Unit1.h:
//---------------------------------------------------------------------------
#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <IdHTTP.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published: // IDE-managed Components
TMemo *Memo1;
TButton *Button1;
TButton *Button2;
TIdHTTP *IdHTTP1;
void __fastcall Button1Click(TObject *Sender);
void __fastcall Button2Click(TObject *Sender);
private: // User declarations
public: // User declarations
__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif
Unit1.cpp:
//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include "Unit1.h"
#include <System.Sysutils.hpp>
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
IdHTTP1->Head("http://dsrt.dyndns.org/files/MAIN.zip");
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->Date));
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->Expires));
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->LastModified));
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button2Click(TObject *Sender)
{
TDateTime dt = ...; // assign some value
// see functions such as Date(), Now(), EncodeDateTime(), etc,
// or use the TDateTimePicker component...
System::String str = DateToStr(dt);
IdHTTP1->Head("http://dsrt.dyndns.org/files/MAIN.zip");
if (DateToStr(IdHTTP1->Response->Date) != str)
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->Date));
if (DateToStr(IdHTTP1->Response->Expires) != str)
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->Expires));
if (DateToStr(IdHTTP1->Response->LastModified) != str)
Memo1->Lines->Add(DateTimeToStr(IdHTTP1->Response->LastModified));
}
//---------------------------------------------------------------------------
That being said, using strings to compare date/time values is not a good idea in general. Such strings are subject to locale issues. You are using conversion functions that are dependent on the local machine's current locale, not HTTP's standardized date/time formats. The TIdHTTP properties you are using are TDateTime values, where TIdHTTP has already translated the HTTP-provided values into binary values in local date/time (based on the local machine's current timezone). You can compare those values as-is without worrying about any string conversions, eg:
void __fastcall TForm1::Button2Click(TObject *Sender)
{
TDateTime dt = ...; // assign some value
// see functions such as Date(), Now(), EncodeDateTime(), etc,
// or use the TDateTimePicker component...
IdHTTP1->Head("http://dsrt.dyndns.org/files/MAIN.zip");
if (IdHTTP1->Response->Date != dt)
{
//...
}
if (IdHTTP1->Response->Expires != dt)
{
//...
}
if (IdHTTP1->Response->LastModified != dt)
{
//...
}
}
Doing TDateTime comparisons is much more accurate and reliable than string comparisons. And you are not limited to just the == and != operators, you can use the < and > operators as well:
void __fastcall TForm1::Button2Click(TObject *Sender)
{
TDateTime dt = Date();
IdHTTP1->Head("http://dsrt.dyndns.org/files/MAIN.zip");
if (IdHTTP1->Response->Date < dt)
{
// older than today...
}
if (IdHTTP1->Response->Expires < dt)
{
// expired prior to today...
}
if (IdHTTP1->Response->LastModified < dt)
{
// last modified prior to today...
}
}