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].

PictureBox* picBlocks[];
should be
PictureBox* picBlocks[5];

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

and

at this line:

Code:

---

picBlocks[i] = new PictureBox();

---

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

Quote:

---

Originally Posted by tineras

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() );

---

---

Yes that is what I mean

Quote:

---

Originally Posted by tineras

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

---

I think if you still have to access the the PictureBoxes in the same function then there should be a way to access them via pnlGameField->Controls
Even if you do as Shakti says the pointer- array would go out of scope after return from that function.
Kurt

EDIT: Just saw that this is not C++ ( seems to be some garbage collector involved ) so I actually don't know anything about scopes in your system.

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.

Quote:

---

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

Quote:

---

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

Quote:

---

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

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.

Quote:

---

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;

---

Why are you including both cmath and math.h? I'd imagine if you opened math.h, you would see a small library that includes cmath and directs the use of all of it's functions under the std namespace.

Anyway, I don't know the API you are using, so I'm not familiar with the add() method you have there. Does it take a PictureBox or a PictureBox*? If it's the latter, then use the second code I gave you.

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