I want to implement a collection or list using TOwnedCollection / TCollectionItem. I need a persistent list (to load and create from a FileStream) of classes with polymorphism.
Here is (part of) my code so far, but I didn't succeed to create the derived class TGenerator instead of its parent TPowerComponent and add it to the Collection.
//-------------------------------------------------------------------------------------
class TPCCollection : public TOwnedCollection
{
typedef TOwnedCollection inherited;
private:
TPowerComponent* __fastcall GetPowerComponent(int Index);
void __fastcall SetPowerComponent(int Index, TPowerComponent *Value);
public:
__fastcall TPCCollection(TPersistent *Owner);
HIDESBASE TPowerComponent* __fastcall Add(void);
HIDESBASE TPowerComponent* __fastcall Insert(int Index);
__property TPowerComponent* PCCollection[int Index] = {read=GetPowerComponent, write=SetPowerComponent};
};
//-------------------------------------------------------------------------------------
class TPowerComponent : public TCollectionItem
{
typedef TCollectionItem inherited;
public :
int X, Y, Rotation;
PowSymbType HisType;
__fastcall TPowerComponent(TCollection *Collection, PowSymbType AType );
void __fastcall Assign(TPersistent *Source);
virtual void __fastcall Paint(TCanvas * Canvas);
};
//-------------------------------------------------------------------------------------
class TGenerator : public TPowerComponent
{
typedef TPowerComponent inherited;
public :
double PG, Qgmin, Qgmax, Vsch;
__fastcall TGenerator(TCollection *Collection, PowSymbType AType );
void __fastcall Assign(TPersistent *Source);
virtual void __fastcall Paint(TCanvas * Canvas);
};
//-------------------------------------------------------------------------------------
// implementation
//-------------------------------------------------------------------------------------
// TPCCOllection
//-------------------------------------------------------------------------------------
__fastcall TPCCollection::TPCCollection(TPersistent *Owner)
: TOwnedCollection(Owner, __classid(TPowerComponent))
{
}
//-------------------------------------------------------------------------------------
TPowerComponent* __fastcall TPCCollection::Add()
{
return static_cast<TPowerComponent>(inherited::Add());
}
//-------------------------------------------------------------------------------------
TPowerComponent* __fastcall TPCCollection::Insert(int Index)
{
return static_cast<TPowerComponent>(inherited::Insert(Index));
}
//-------------------------------------------------------------------------------------
TPowerComponent* __fastcall TPCCollection::GetPowerComponent(int Index)
{
return static_cast<TPowerComponent>(inherited::GetItem(Index));
}
//-------------------------------------------------------------------------------------
void __fastcall TPCCollection::SetPowerComponent(int Index, TPowerComponent *Value)
{
inherited::SetItem(Index, Value);
}
//-------------------------------------------------------------------------------------
// TPowerComponent
//-------------------------------------------------------------------------------------
__fastcall TPowerComponent::TPowerComponent(TCollection *Collection, PowSymbType AType )
: TCollectionItem(Collection)
{
HisType=AType;
Rotation=0;
}
//-------------------------------------------------------------------------------------
void __fastcall TPowerComponent::Assign(TPersistent *Source)
{
TPowerComponent *Src = dynamic_cast<TPowerComponent>(Source);
if( Src )
{
// copy members from Src...
}
else inherited::Assign(Source);
}
//-------------------------------------------------------------------------------------
// se dessine
void __fastcall TPowerComponent::Paint(TCanvas * Canvas)
{
...
}
//-------------------------------------------------------------------------------------
// TGenerator
//-------------------------------------------------------------------------------------
__fastcall TGenerator::TGenerator(TCollection *Collection, PowSymbType AType )
:TPowerComponent( Collection, AType )
{
PG=0; Qgmin=0; Qgmax=0; Vsch=1.0; Con=-1;
}
//-------------------------------------------------------------------------------------
void __fastcall TGenerator::Assign(TPersistent *Source)
{
TGenerator *Src = dynamic_cast<TGenerator>(Source);
if( Src )
{
// copy members from Src...
}
else inherited::Assign(Source);
}
//-------------------------------------------------------------------------------------
// Usage
TPCCollection * NetWork = new TPCCollection(this);
// Usage to Access all the collection
for( int i=0; i< NetWork->Count; i++)
{
((TPowerComponent*)(NetWork->Items[i]))->Paint(Canvas);
}
To add a TGenerator and not a TPowerComponent, I use:
TGenerator * Gen=new TGenerator( NetWork, Generator);
The creation of the TCollectionItem child automatically add itself to the TCollection
The problem here is that we can't separate the process of item creation from adding it to the collection.
When I need another list that can have some of the items of the first collection list, for example, SelectedComponents can have one or some of the Items of the NetWork Collection, without recreating them.
This can be done with
std::list<TPowerComponent*> SelectedComponents;
but I can't write/read them using FileStream / persistent list. I need to put them in a TCollection but without recreating them.
How?
The RTL's native DFM streaming for TCollection objects only partially supports polymorphic TCollectionItem classes.
You can add polymorphic TCollectionItem objects to a TCollection in code (at runtime, as well as at design-time with the aid of a custom editor), as long as they all derive from a common base class that is passed to the TCollection constructor. And such a collection can even be saved as-is to a DFM.
However, when loading back a DFM, native streaming will force all collection items read from the DFM to use whatever TCollectionItem class type you pass to the TCollection constructor. So, polymorphic classes can't be loaded natively.
The only way to override that behavior is to disable native streaming for the collection (make your TCollection property be non-published, or at least mark it as stored=false), and then stream the collection items manually.
Have your main component (or whatever TPersistent class owns the collection) override the virtual DefineProperties() method to call TFiler.DefineProperty() to register custom reading/writing methods for streaming the collection items. To support polymorphic classes, you will have to write each item's ClassName to the DFM before writing its property values, then read the name back so you know which class to instantiate before then reading property values.
Related
There is a library for parsing.
I added ALXmlDoc.pas to the project, C++Builder created ALXmlDoc.hpp
In ALXmlDoc.pas lines 177,178:
property Nodes [const Name: AnsiString]: TALXMLNode read GetNodeByName; default;
property Nodes [const Index: integer]: TALXMLNode read GetNodeByIndex; default;
In ALXmlDoc.hpp:
__property TALXMLNode * Nodes [const System :: AnsiString Name] = {read = GetNodeByName / *, default */};
__property TALXMLNode * Nodes [const int Index] = {read = GetNodeByIndex};
I get an error about duplication - how to fix it?
In .pas line 705
property OnParseText: TAlXMLParseTextEvent read FonParseText Write FonParseText; // [added from TXMLDocument]
In ALXmlDoc.hpp:
__property _di_TAlXMLParseTextEvent OnParseText = {read = FonParseText, write = FonParseText};
__interface TAlXMLParseTextEvent: public System :: IInterface
{
virtual void __fastcall Invoke (System :: TObject * Sender, const System :: AnsiString Path, const System :: AnsiString Str) = 0;
};
private:
_di_TAlXMLParseTextEvent FonParseText;
protected:
void __fastcall DoParseText (const System :: AnsiString Path, const System :: AnsiString Str);
In my Unit1.h:
void __fastcall OnParseText (System :: TObject * Sender, const System :: AnsiString Path, const System :: AnsiString Str);
In my Unit1.cpp:
void __fastcall TForm1 :: OnParseText (System :: TObject * Sender, const System :: AnsiString Path, const System :: AnsiString Str)
{
ShowMessage(Str);
}
// ------------------------------------------------ ---------------------------
void __fastcall TForm1 :: Button1Click (TObject * Sender)
{
TALXMLDocument * aXMLDocument = new TALXMLDocument ("root");
aXMLDocument-> OnParseText = OnParseText;
}
I get an error:
[bcc32 Error] Unit1.cpp (30): E2235 Member function must be called or its address taken
How to declare an event?
In C++, array properties can't be overloaded solely on their index type. So you will have to rename one of the offending properties, there is no other option. And then I would suggest you file a report with the library author asking to make the library be more friendly to C++ users.
In the Delphi code, TAlXMLParseTextEvent is a reference to an anonymous method:
TAlXMLParseTextEvent = reference to procedure (Sender: TObject; const Path, Str: AnsiString);
Which is why it gets translated to an __interface on the C++ side (because anonymous methods really are implemented behind the scenes using interfaces). Delphi-style anonymous methods require extra handling in C++, as is documented on Embarcadero's DocWiki:
How to Handle Delphi Anonymous Methods in C++
Under the cover, Delphi implements anonymous methods types (also known as method references) via an interface that implements an Invoke(...) method.
So a method that takes a method reference parameter in Delphi is exposed to C++ as a method that takes an interface.
As such, your C++ code would need to do something more like this instead:
struct TParseTextMethod
{
void operator()(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
ShowMessage(Str);
}
};
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
TALXMLDocument *aXMLDocument = new TALXMLDocument("root");
// the TMethodRef functor is defined in the documentation,
// you can copy/paste it as-is into your code...
typedef TMethodRef<TAlXMLParseTextEvent,
TParseTextMethod,
void,
TObject *Sender,
const AnsiString,
const AnsiString> MyMethRef;
aXMLDocument->OnParseText = _di_TAlXMLParseTextEvent(new MyMethRef(TParseTextMethod()));
}
Or, you can streamline the functor usage a bit more by not using the TMethodRef wrapper (see Inheritance and Interfaces and Implementing Interfaces):
class TParseTextMethod : public TCppInterfacedObject<TAlXMLParseTextEvent>
{
public:
TParseTextMethod() {}
INTFOBJECT_IMPL_IUNKNOWN(TInterfacedObject);
void __fastcall Invoke(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
ShowMessage(Str);
}
};
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
TALXMLDocument *aXMLDocument = new TALXMLDocument("root");
aXMLDocument->OnParseText = _di_TAlXMLParseTextEvent(new TParseTextMethod());
}
Or, if you want to keep using your OnParseText() method as-is, then you will have to wrap it inside a functor, eg:
void __fastcall TForm1::OnParseText(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
ShowMessage(Str);
}
//------------------------------------------------ ---------------------------
typedef void __fastcall (__closure *TAlXMLParseTextMethod)(TObject *Sender, const AnsiString Path, const AnsiString Str);
struct TParseTextMethod
{
TAlXMLParseTextMethod Method;
TParseTextMethod(TAlXMLParseTextMethod aMethod) : Method(aMethod) {}
void operator()(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
Method(Sender, Path, Str);
}
};
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
TALXMLDocument *aXMLDocument = new TALXMLDocument("root");
typedef TMethodRef<TAlXMLParseTextEvent,
TParseTextMethod,
void,
TObject *Sender,
const AnsiString,
const AnsiString> MyMethRef;
aXMLDocument->OnParseText = _di_TAlXMLParseTextEvent(new MyMethRef(TParseTextMethod(&OnParseText)));
}
Or:
void __fastcall TForm1::OnParseText(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
ShowMessage(Str);
}
//------------------------------------------------ ---------------------------
typedef void __fastcall (__closure *TAlXMLParseTextMethod)(TObject *Sender, const AnsiString Path, const AnsiString Str);
class TParseTextMethod : public TCppInterfacedObject<TAlXMLParseTextEvent>
{
public:
TAlXMLParseTextMethod Method;
TParseTextMethod(TAlXMLParseTextMethod aMethod) : Method(aMethod) {}
INTFOBJECT_IMPL_IUNKNOWN(TInterfacedObject);
void __fastcall Invoke(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
Method(Sender, Path, Str);
}
};
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
TALXMLDocument *aXMLDocument = new TALXMLDocument("root");
aXMLDocument->OnParseText = _di_TAlXMLParseTextEvent(new TParseTextMethod(&OnParseText));
}
Alternatively, if you are using one of the Clang-based compilers then you can use a C++ style lambda instead of a functor:
void __fastcall TForm1::Button1Click(TObject *Sender)
{
TALXMLDocument *aXMLDocument = new TALXMLDocument("root");
aXMLDocument->OnParseText = [](TObject*, const AnsiString, const AnsiString Str) {
ShowMessage(Str);
};
}
Or:
void __fastcall TForm1::OnParseText(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
ShowMessage(Str);
}
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
TALXMLDocument *aXMLDocument = new TALXMLDocument("root");
aXMLDocument->OnParseText = [this](TObject *Sender, const AnsiString Path, const AnsiString Str) {
OnParseText(Sender, Path, Str);
};
}
I need access to TControlItem.InternalSetLocation which is protected. I Delphi you would do
type
THackControlItem = class(TControlItem);
How do you do this in C++ Builder?
As in Delphi, you need to inherit the class but also override and make public the protected function. However, I wouldn't recommend to use it in production code.
class THackControlItem : public TControlItem
{
public:
void __fastcall InternalSetLocation(int AColumn, int ARow, bool APushed, bool MoveExisting)
{
TControlItem::InternalSetLocation(AColumn, ARow, APushed, MoveExisting);
}
};
In the program
TControlItem* ci = ...;
static_cast<THackControlItem*>(ci)->InternalSetLocation(...);
This is a nice trick I think Remy Lebeau showed me but can not find the QA anymore...
//---------------------------------------------------------------------------
#ifndef _TDirectMemoryStream
#define _TDirectMemoryStream
class TDirectMemoryStream:TMemoryStream // just for accessing protected SetPointer
{
public:
void SetMemory(BYTE *ptr,DWORD siz) { SetPointer(ptr,siz); Position=0; };
};
#endif
//---------------------------------------------------------------------------
You simply create new class that is descendant of the class you want to access. Now just add get/set functions for the protected members ...
Now usage:
TMemoryStream *mem=new TMemoryStream(); // original class instance you want to access
// overtype to our new class and access/use you get/set ...
((TDirectMemoryStream*)(mem))->SetMemory(hdr->lpData,hdr->dwBytesUsed);
delete mem; // release if not needed anymore
I am using it btw to feed a memory stream with custom memory data hdr coming from vfw camera so I can properly decode it using TJPEGImage class instead of writing the data into file and loading it back each frame ...
Here another example:
class A
{
protected:
int x;
public:
int getx(){ return x; }
};
class hack_A:A
{
public:
void setx(int _x){ x=_x; }
};
void test()
{
A a;
hack_A *ha=(hack_A*)&a;
ha->setx(10);
a.getx(); // print the x somwhere
}
However this will not work for private members ... In such case its doable too but requires access to A source code:
class A
{
protected:
int x;
private:
int y;
public:
int getx(){ return x; }
int gety(){ return y; }
friend class hack_A; // but this one requires access to A soourcecode
};
class hack_A:A
{
public:
void setx(int _x){ x=_x; }
void sety(int _y){ y=_y; }
};
void test()
{
A a;
hack_A *ha=(hack_A*)&a;
ha->setx(10);
ha->sety(20);
a.getx(); // print the x somwhere
a.gety(); // print the x somwhere
}
The accepted answer in this question shows how to check for and use an interface on a VCL-derived object in Delphi.
How to use Interface with VCL Classes - Part 2
procedure Test;
var
O1: TSomeThing;
Intf: ISomething;
begin
O1 := TSomeThing.Create(nil);
if Supports(O1, ISomething, Intf) then
begin
Intf.DoSomething;
end;
Basically, I want to do the same in C++Builder but haven't worked out how to use "Supports" from C++.
Attempting to use <dynamic_cast> fails at compile time when using VCL-derived classes...
TSomeThing * O1;
ISomething *i = dynamic_cast<ISomething*>(O1); // Error: Can't cast
The suggested Inheritance and Interfaces article mentions TObject::GetInterface() but when I try that I get an error "Pure Virtual Function called".
_di_IFoo mc;
if (this->GetInterface(mc)) ...
Update: First, the objects I'm adding interfaces to are existing VCL controls so NOT derived from TInterfacedObject.
Second - there's no COM involved - I hope! The use of Interfaces is purely to allow me to use the concept of interfaces for multiple inheritance with VCL components which C++Builder (at least, in 2010) does not support.
So my interface looks like this (NOTE that there's no __addref/__release etc...):
__interface INTERFACE_UUID("{C527B88F-3F8E-1134-80e0-01A04F57B270}") IMyInterface : public IInterface
{
public:
virtual UTF8String getHello() = 0;
};
And my objects looks like this
class TMyPanel: public TPanel, IMyInterface
{
...
public:
UTF8String getHello() { return "Hello from a TMyPanel";}
...
};
class TMyLabel: public TLabel, IMyInterface
{
...
public:
UTF8String getHello() { return "Hello from a TMyLabel";}
...
};
That's straightforward, and as described in the Embarcadero docs for Interfaces.
But, how to tell if a particular TObject supports IMyInterface???
The following template function does this for me, based on TObject.GetInterfaceEntry() from system.pas:
template<typename T>
T* getInterface(TObject *obj)
{
T *intf = NULL;
PInterfaceEntry interfaceEntry = obj->GetInterfaceEntry(__uuidof(T) );
if (interfaceEntry && interfaceEntry->IOffset != 0)
{
intf = (T*)(((char *)obj) + interfaceEntry->IOffset);
}
return intf;
}
And we use it like this:
IMyInterface *myIf = getInterface<IMyInterface>(aRandomTObject);
if (myIf)
{
UTF8String s = myIf->getHello();
}
Please let me know if there's a better way than this, as the VTable/Pointer spelunking makes my teeth itch...
You do it the same way in C++ as in Delphi - via the Sysutils::Supports() function.
This works for me when I try it:
//---------------------------------------------------------------------------
#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
#include <Vcl.ExtCtrls.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published: // IDE-managed Components
void __fastcall FormClick(TObject *Sender);
private: // User declarations
TPanel *p;
TLabel *l;
void Test();
public: // User declarations
__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif
//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm7 *Form1;
//---------------------------------------------------------------------------
__interface INTERFACE_UUID("{C527B88F-3F8E-1134-80e0-01A04F57B270}") IMyInterface : public IInterface
{
public:
virtual UTF8String getHello() = 0;
};
#if !defined(INTFOBJECT_IMPL_IUNKNOWN)
#define INTFOBJECT_IMPL_IUNKNOWN(BASE) \
ULONG __stdcall AddRef() { return BASE::_AddRef();} \
ULONG __stdcall Release(){ return BASE::_Release();} \
HRESULT __stdcall QueryInterface(REFIID iid, void** p){ return BASE::QueryInterface(iid, p);}
#endif
class TMyPanel : public TPanel, public IMyInterface
{
INTFOBJECT_IMPL_IUNKNOWN(TPanel)
public:
__fastcall TMyPanel(TComponent *Owner) : TPanel(Owner) {}
UTF8String getHello() { return "Hello from a TMyPanel"; }
};
class TMyLabel : public TLabel, public IMyInterface
{
INTFOBJECT_IMPL_IUNKNOWN(TLabel)
public:
__fastcall TMyLabel(TComponent *Owner) : TLabel(Owner) {}
UTF8String getHello() { return "Hello from a TMyLabel"; }
};
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
: TForm(Owner)
{
p = new TMyPanel(this);
p->Parent = this;
l = new TMyLabel(this);
l->Parent = p;
l->Caption = L"Test";
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormClick(TObject *Sender)
{
Test();
}
//---------------------------------------------------------------------------
void TForm1::Test()
{
DelphiInterface<IMyInterface> Intf;
if (Supports(p, __uuidof(IMyInterface), (void*)&Intf))
{
UTF8String s = Intf->getHello();
ShowMessage(s);
Intf.Release();
}
if (Supports(l, __uuidof(IMyInterface), (void*)&Intf))
{
UTF8String s = Intf->getHello();
ShowMessage(s);
Intf.Release();
}
}
//---------------------------------------------------------------------------
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.
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...
}
}
I'm using Builder C++ 6.
in the folowing code I want my function KreirajPOlja() to generate random AnsiString characters on the buttons but what i always gain is just matrix 9*9 with just one generated character as in the picture:
void __fastcall TForm1::KreirajPolja()
{
int tr;
for(int i=0;i<dim_x;i++)
for(int j=0;j<dim_y;j++) {
Dugme[i][j]->Height=20;
Dugme[i][j]->Width=Dugme[i][j]->Height;
Dugme[i][j]->Left=i*Dugme[i][j]->Height;
Dugme[i][j]->Top=j*Dugme[i][j]->Height;
Dugme[i][j]->Parent=this;
tr=PostaviRandom();
Dugme[i][j]->Caption= NizSlova[tr];
}
Button1->Caption="submit";
Button1->Enabled=false;
Form1->Width=dim_x* 20+5;
Form1->Height=(dim_y+2)* 20+25;
}
//---------------------------------------------------------------------------
int __fastcall TForm1::PostaviRandom(){
int k;
srand(time(0));
k=rand()%sizeof(NizSlova);
return k;}
and here is the folowing cpp code
#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
#include <time.h>
//--- ------------------------------------------------------------------------
class TForm1 : public TForm
{
__published: // IDE-managed Components
TButton *Button1;
void __fastcall FormCreate(TObject *Sender);
public: // User declarations
TButton*** Dugme;
TImage *** Slike;
TEdit *brojac;
int dim_x, dim_y;
int vrijeme,kr;
int BrojSlova, br;
AnsiString NizSlova;
__fastcall TForm1(TComponent* Owner);
void __fastcall KreirajSlova();
void __fastcall AlocirajProstor();
void __fastcall BrisiProstor();
void __fastcall AlocirajProstorZaSlova();
void __fastcall BrisiProstorZaSlova();
void __fastcall KreirajPolja();
virtual int __fastcall PostaviRandom();
AnsiString __fastcall DajSlovo();
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif
Don't call srand in your loop. Call it once at the start of the program.
Each time you call srand you reset the random number generator. Since you call it with the same parameter each time (your code runs in less than a second so the value of time(NULL) doesn't change), you get the same result from rand().
There is no need to call srand multiple times in the same program unless you intentionally want to reproduce an old sequence of random numbers.