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How to create an array of buttons in Borland C ++ Builder and work with it?

Specific question

How to create an array of buttons in Borland C ++ Builder and work with it?

I am using Borland C ++ Builder 6 and Borland Developer Studio 2006 (Turbo C ++ 2006).

purpose

To work with a lot of buttons on a form, just using a for loop with an index, for example changing their title, size and position.

I know if I have a button named Button1

and inside the click event of that button, if I create another button (via TButton *Button2 = new TButton(Form1)

) I can assign Button1

to Button2

( Button2 = Button1

) and these I can just change the title Button1

with Button2->Caption

. So I would like to expand on it by assigning real component pointers to array elements so that they work with all of them with a loop for

.

Ok if someone found a way to add all buttons as an array in the form, better :)

Trying to

The following tests were run by placing the appropriate code in TForm1 :: Button1Click (), the button event on the form:

  • Test 1

    • Description: Create an array directly

    • Code:

      TButton Buttons[3];

    • Result: Compilation error:

      > [C++ Error] Unit1.cpp(23): E2248 Cannot find default constructor
> to initialize array element of type 'TButton'
    • Comments:
      • I've tested several variants of this test (for example, TButton Buttons = new TButton[3]

        working with a function calloc

        , etc.), but they all point to the problem that TButton

        there is no no-argument constructor, i.e. TButton()

        , but only TButton (TComponent *AOwner)

        , TButton(void *ParentWindow)

        and TButton(const TButton &)

        ;
      • Any way to use operator new

        with arguments for constructor prototypes TButton

        for an array?

  • Test 2

    • Description: Create a vector

    • Code: Also add #include "vector.h"

      to the block header ...

      vector<TButton> Buttons;
Buttons[0].Caption="it is ok";
Buttons[1].Caption="mayday, mayday";

    • Result: Debugger exception on third line:

      > Project Project1.exe raised exception class EAccessViolation
> with message 'Acceess violation at address 401075B9 in module
> 'vcl60.bpl'. Read of address 00000254'. Proccess stopped. Use
> Step or Run to continue.
    • Comments:
      • Yes, I expected it to be raised, but I put it here for someone to tell how to allocate memory for more elements on this vector after creation as it vector<TButton> Buttons(3);

        doesn't work for the same reason as test1 failed :(

General question

How do I do this for any visual component?

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2 answers


All your attempts have failed for the same reason - you are trying to create an array / vector of actual object instances TButton

instead of an array / vector of pointer instances in TButton

.

To create a fixed-length array of pointer buttons :

TButton* Buttons[3];
...
Buttons[0] = Button1;
Buttons[1] = Button2;
Buttons[2] = Button3;
...
for(index = 0; index < 3; ++index)
{
    TButton *Btn = Buttons[index];
    // use Btn as needed...
}

To create a dynamic-length array of pointer buttons :



TButton** Buttons;
...
Buttons = new TButton*[3];
Buttons[0] = Button1;
Buttons[1] = Button2;
Buttons[2] = Button3;
...
for(index = 0; index < 3; ++index)
{
    TButton *Btn = Buttons[index];
    // use Btn as needed...
}
...
delete[] Buttons;

To create a pointers button vector :

std::vector<TButton*> Buttons;
...
Buttons.push_back(Button1);
Buttons.push_back(Button2);
Buttons.push_back(Button3);
...
for(index = 0; index < 3; ++index)
{
    TButton *Btn = Buttons[index];
    // use Btn as needed...
}
/*
Or:
for(std::vector<TButton*>::iterator iter = Buttons.begin(); iter != Buttons.end(); ++iter)
{
    TButton *Btn = *iter;
    // use Btn as needed...
}
*/
+2


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Wonderful Typedef + Pseudo Array = Solution

  • Wonderful Typedef:

    • After hours of searching, I saw typedef

      this stack overflow and google search network and thought why not:

      typedef TButton* TButtons;

    • Well this changes everything, because I can execute:

      TButtons Buttons[3];

  • Pseudo Array:

    • The problem remained in how to allocate memory for the data stored in this array Buttons[3]

      , but knowing the 2nd paragraph of the "Purpose" section of my question, I thought: forget the new data, the data is there, point to there (this is how I call it to build pseudo-array, because I'm only creating an array of pointers to existing data):

      TButtons Buttons[3] = {Button1, Button2, Button3};
    • Where Button1

      , Button2

      and Button3

      were already created when I placed them in the form normally (via my mouse).


Working example

  • Create a new vcl / forms application project;
  • Place the 3 buttons on the left in the figure below ( Button1

    , Button2

    , Button3

    ) to demonstrate this solution and one large button ( Button4

    ) as shown below to perform an action; the figure bellow point 2

  • Paste the following code when you press the fourth button, the big ( Button4

    );

    typedef TButton* TButtons;
TButtons Buttons[3] = {Button1, Button2, Button3};
int index;

for(index=0;index<3;index++)
{
        Buttons[index]->Caption=(AnsiString)"teste "+index+" - "+(1+random(100));
        Buttons[index]->Left=25+4*random(100);
        Buttons[index]->Top=25+4*random(100);
}
  • Perform "Shazam!" run and play with it ... like a game project
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