Thread: Creating object arrays for VC++

I need to create an array of objects when I click a button in Visual C++. I am having some difficulty doing so. Any help would be appreciated.

---Code within button click---

Code:

PictureBox* picBlocks[];

for(int i = 0; i < 5; i++)
{

picBlocks[i] = new PictureBox();

pnlGameField->Controls->Add(picBlocks[i]);

}

When I run it, it gives me an error about an unhandled exception.

Debug stops at the last line of code. I'm still quite a beginner, so I'm not exactly sure what to look for.

Thanks

You don't allocate any space for the pointer array.
Wouln't that be enough ?

Code:

for(int i = 0; i < 5; i++) 
     pnlGameField->Controls->Add(new PictureBox() );

Kurt

Are you saying that this should be my only line of code:

Code:

for(int i = 0; i < 5; i++) 
     pnlGameField->Controls->Add(new PictureBox() );

I need each new PictureBox to be named picBlocks[i].

Code:

for(int i = 0; i < 5; i++) 
pnlGameField->Controls->Add(new PictureBox() );

This seems to work without error, but I just don't know how to access the new PictureBoxes that are created.

Like PictureBox[0] or PictureBox[1] or whatever they would be called so that I can use them how I wish.

When I add [5] instead of [], I get the error at this line:
Code:

PictureBox* picBlocks[];


error C3616: '5': a size cannot be specified in a __gc array declaration

This is funny. But as I said don't know anything about this "__gc" thingy.
But I guess that should work

Code:

for(int i = 0; i < 5; i++)  {
    PictureBox* picBlock = new PictureBox();
    pnlGameField->Controls->Add( picBlock );
   // here you can work with the newly created block
}

Kurt

Originally Posted by ZuK

This is funny. But as I said don't know anything about this "__gc" thingy.
But I guess that should work

Code:

for(int i = 0; i < 5; i++)  {
    PictureBox* picBlock = new PictureBox();
    pnlGameField->Controls->Add( picBlock );
   // here you can work with the newly created block
}

Kurt

That seems to be running without any problems also, but I'm not sure what each of these new PictureBoxes are being called. I don't know how reference them in my code...

like:

Code:

picBlocks1->Top = 100;

or

PictureBox[1]->Left = 50;

I don't know how to use it once it's created.

In my previous example you would have to do something like this.

Code:

for(int i = 0; i < 5; i++)  {
    PictureBox* picBlock = new PictureBox();
    pnlGameField->Controls->Add( picBlock );
    switch ( i ) {
       case 0: 
            picBlock->Top = 100;
            picBlock->Left = 50;
            break;
       case 1: 
            picBlock->Top = 150;
            picBlock->Left = 50;
            break;
  //       ......
     }
}

I am aware that this is just a workaround. Even in a garbage collected system ther must be a way to create an array of pointers.
Kurt

Originally Posted by ZuK

In my previous example you would have to do something like this.

Code:

for(int i = 0; i < 5; i++)  {
    PictureBox* picBlock = new PictureBox();
    pnlGameField->Controls->Add( picBlock );
    switch ( i ) {
       case 0: 
            picBlock->Top = 100;
            picBlock->Left = 50;
            break;
       case 1: 
            picBlock->Top = 150;
            picBlock->Left = 50;
            break;
  //       ......
     }
}

I am aware that this is just a workaround. Even in a garbage collected system ther must be a way to create an array of pointers.
Kurt

I tried this and it does work. However, I am still unable to use these items in other functions in my code. I really need to be able to reference them individually without having to jump through a lot of hoops to make it work.

Aaron

Originally Posted by SlyMaelstrom

You aren't passing anything to the constructors, so what's wrong with:

Code:

PictureBox* picBlocks = new PictureBox[5];

for(int i = 0; i < 5; i++)
   pnlGameField->Controls->Add(picBlocks[i]);

EDIT: Oh, wait. Do you want an array of pointers?

Maybe change your "PictureBox* picBlocks[]" to "PictureBox** picBlocks" and allocate the same way. Like this:

Code:

PictureBox **picBlocks = new PictureBox*[5]; // Pointer to array of 5 pointers

for(int i = 0; i < 5; i++)
   pnlGameField->Controls->Add(picBlocks[i]);

EDIT 2: Sorry for all the edits, hope I'm not screwing with your head if you're looking at it right now.

When I put this code in:

Code:

PictureBox* picBlocks = new PictureBox[5];

for(int i = 0; i < 5; i++)
   pnlGameField->Controls->Add(picBlocks[i]);

I get a bunch of errors:
---------------------------
error C2691: 'System::Windows::Forms::PictureBox' : invalid type for __gc array element

error C2691: 'System::Windows::Forms::PictureBox __gc *' : invalid type for __gc array element

error C3149: 'System::Windows::Forms::PictureBox' : illegal use of managed type 'System::Windows::Forms::PictureBox'; did you forget a '*'?

error C3262: invalid array indexing: 1 dimension(s) specified for 5-dimensional 'System::Windows::Forms::PictureBox __gc * __gc[,,,,]'

error C3616: '5': a size cannot be specified in a __gc array declaration
--------------------------

Is there something missing at the top of my code that I might need for this to work.

I have:

Code:

#pragma once
#include <iostream>
#include <cmath>
#include <math.h>
using namespace std;

There seem to be very different rules for pointer arrays in "managed C++" code. Guess you should look for a forum that specifically deals with this kind of "C++ extension"
Kurt