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Dec 25th, 2008

Borland C++ Builder 6 : creating new objects - HOW ??

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Hi, I am trying to make small game , but I am confronting with a problem. I have a function that should add a new button to my form when it's called. The problem is that I don't know how to create a new object (a button, a shape or whatever...) and adding it to my form. In Java, this would be fairly simple, but how do I it here ? my header file contains the form class:

(Toggle Plain Text)

class TForm1 : public TForm
{
__published:	// IDE-managed Components
        TShape *Shape1;
        TButton *Button1;
        void __fastcall Button1Click(TObject *Sender);
private:	// User declarations
public:		// User declarations
             TButton *TestBtn ;
        __fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;

At public I've added a test button (TestBtn). The same problem: how can use it ? It must be first allocated (and how)?

Thanx !

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

c++ Syntax (Toggle Plain Text)
//...
void __fastcall TForm1::example(void)
{
     TestBtn = new TButton();
     TestBtn->Visible = false;
}
//...
void __fastcall TForm1::example(void)
{
     TestBtn = new TButton();
     TestBtn->Visible = false;
}

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

Still doesn't work !It gives me this error :
" E2285 Could not find a match for 'TButton::TButton()' "

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

Header required for 'TButton' is missing i think.

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

TButton's constructor needs to be passed a pointer to a TComponent (eg a parent form) that is responsible for managing the button.

It is also necessary to set various attributes: position, caption, visibility, the function to be called when the newly created button is created, etc etc. TButton is derived from TWinControl, so some inherited attributes probably also need to be set.

It would probably be easier to create a button on your form at design time, and have your function make that button visible as needed.

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

c++ Syntax (Toggle Plain Text)
TestBtn = new TButton(this);
TestBtn->Parent = this;
TestBtn->Caption = "Check";
TestBtn = new TButton(this);
TestBtn->Parent = this;
TestBtn->Caption = "Check";

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

Ok , this sorted things out a little bit. My next problem is, how to assign each button a different function when it's pressed.For example I do something like this:

(Toggle Plain Text)

for (x = 0; x < 10; x++)
{
TButton *TestBtn = new TButton(this);
TestBtn->Caption = "My button " + IntToStr(x);
TestBtn->Top = 100;
TestBtn->Left = 100 + 10 * x;
TestBtn->OnClick = myfunction(x);
TestBtn->Parent = this;
}

where myfunction is defined like this in the header file:

(Toggle Plain Text)

void __fastcall TForm1::myfunction(int x)
{
ShowMessage("Button " + IntToStr(x) + " clicked");
}

I get an "Not an allowed type" error when compiling. It seems that I can't pass a variable like this to myfunction. But, if I do like this: TestBtn->OnClick = myfunction; with myfunction looking now :

(Toggle Plain Text)

void __fastcall TForm1::myfunction(TObject *Sender)
{
ShowMessage("Button ? clicked");
}

it works, but it doesn't do what I wanted it to do.But how do I know which of the ten buttons is clicked now? How can I pass this information to the function?

Thanx,
Adrian

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

c++ Syntax (Toggle Plain Text)
 
class TForm1:public TForm
{
      private:
           // create temp var..
           int m_x;
      //...
};
 
void __fastcall TForm1::myfunction1(int x)
{
     ShowMessage("Button " + IntToStr(x) + " clicked");
}
 
void __fastcall TForm1::myfunction(TObject *Sender)
{
     myfunction1(m_x);
}
 
//######################################
 
TButton *TestBtn = new TButton(this);
TestBtn->OnClick = myfunction;
TestBtn->Parent = this;
 
for (x = 0; x < 10; x++)
{
    TestBtn->Caption = "My button " + IntToStr(x);
    TestBtn->Top = 100;
    TestBtn->Left = 100 + 10 * x;
    m_x = x;
    TestBtn->OnClick(this/*sender*/);
}
//######################################
class TForm1:public TForm
{
      private:
           // create temp var..
           int m_x;
      //...
};

void __fastcall TForm1::myfunction1(int x)
{
     ShowMessage("Button " + IntToStr(x) + " clicked");
}

void __fastcall TForm1::myfunction(TObject *Sender)
{
     myfunction1(m_x);
}

//######################################

TButton *TestBtn = new TButton(this);
TestBtn->OnClick = myfunction;
TestBtn->Parent = this;

for (x = 0; x < 10; x++)
{
    TestBtn->Caption = "My button " + IntToStr(x);
    TestBtn->Top = 100;
    TestBtn->Left = 100 + 10 * x;
    m_x = x;
    TestBtn->OnClick(this/*sender*/);
}
//######################################

Last edited by cikara21; Dec 26th, 2008 at 5:23 pm.

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

This works only if the buttons are clicked immediately after they're created.After that that , any button I click , it shows the same : "Button 9 clicked" (and that's logic, m_x has the latest value, and that's 9). How to do , to stick to each button it's attributes(here, it's id) ?

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Dec 26th, 2008

Re: Borland C++ Builder 6 : creating new objects - HOW ??

try yhis...

c++ Syntax (Toggle Plain Text)
 
//######################################
 
class TForm1:public TForm
{
    //...
    public:
        TButton *TestBtn[10]
    //...
};
 
//######################################
 
for (x = 0; x < 10; x++)
{
     TestBtn[i] = new TButton(this);
     TestBtn[i]->Parent = this;
     TestBtn[i]->OnClick = myfunction;
     TestBtn[i]->Caption = "My button " + IntToStr(x);
     TestBtn[i]->Top = 100;
     TestBtn[i]->Left = 100 + 10 * x;
     m_x = x;
}
 
//######################################
//######################################

class TForm1:public TForm
{
    //...
    public:
        TButton *TestBtn[10]
    //...
};

//######################################

for (x = 0; x < 10; x++)
{
     TestBtn[i] = new TButton(this);
     TestBtn[i]->Parent = this;
     TestBtn[i]->OnClick = myfunction;
     TestBtn[i]->Caption = "My button " + IntToStr(x);
     TestBtn[i]->Top = 100;
     TestBtn[i]->Left = 100 + 10 * x;
     m_x = x;
}

//######################################

Last edited by cikara21; Dec 26th, 2008 at 7:11 pm.

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