C++ Builder Delete Objects of dynamic Array - c++

Question

I want to delete old images I created in a for loop.
The first time clicking the Button the images are created. The second time or third, whatever, the old Images that were created should now be deleted (before the loop) and then directly recreated in the loop.
Because I am getting the Image properties from the database and when someone changed something in the database you should be enabled to get the newest Image properties from the database.
I tried it with delete Image[i], free() and delete[] (whole Array) but I am always getting an Access Violation Error. Here is my following code:
TImage *Image[c]= ; //c is 5
I want to delete the old Images here and then create the new in the loop below
for (int i = 0; i < c; i++)
{
str = " Test "
Image[i] = new TImage(this);
Image[i]->Parent = BoardItem ;
Image[i]->Height = 20 ;
Image[i]->Width = 20 ;
Image[i]->Position->X = d ; // The program asks you the coordinate at the begining of a new loop
Image[i]->Position->Y = e ;
Image[i]->Bitmap = Icon->Bitmap ;
Image[i]->StyleName = str ;
Image[i]->OnClick = ImageClick ;
}

Answer 1

#Mykola i pulled the example out of my code , so it is not that complicated to understand. in button2 i want to delete now all images that are on tabitem1
void __fastcall TForm2::Button2Click(TObject *Sender)
{
TImage *Image[5] ;
for (int i = 0; i < c; i++) {
Image[i] = new TImage(this);
Image[i]->Parent = TabItem1 ;
Image[i]->Height = 20 ;
Image[i]->Width = 20 ;
Image[i]->Position->X = 10 ;
Image[i]->Position->Y = 10 ;
Image[i]->Bitmap = Image1->Bitmap ;
Image[i]->StyleName = "Something" ;
Image[i]->OnClick = ImageClick ;
}
}
//--------------------------------------------------------------------------
void __fastcall TForm2::ImageClick(TObject *Sender)
{
TImage *Img = dynamic_cast<TImage *>(Sender);
ShowMessage(Img->StyleName);
}
//--------------------------------------------------------------------------
void __fastcall TForm2::Button1Click(TObject *Sender)
{
}

Answer 2

You must delete single image by simple delete operator like:
for (int i = 0; i < c; i++)
{
delete Image[i];
// NULL deleted pointer
Image[i] = NULL;
}
Access Violation also may be caused because you still use this images somewhere in your code. And why did you want delete this images? As they are pointers you may simple renew values.
To reserve values for unpredictable amount of pointers TImage* you can use:
TImage** ppImage= NULL;
than create amount of pointers you want:
ppImage = new TImage*[c];
after that you may work with those pointers like you did before.

Answer 3

You could go like this. In the header of the class you define the array and some methods:
int c; // Maximum (better as define?)
TImage *Image[];
bool CheckImagesLoaded();
void DeleteAllImages();
void CreateImage(int nIndex, AnsiString str);
void CreateAllImages();
Then, in the constructor you init the array:
c = 5;
for (int i = 0; i < c; i++)
{
Image[i] = NULL;
}
Now you can do the check if images were already loaded:
bool TForm1::CheckImagesLoaded()
{
return Image[0]!=NULL;
}
To delete them all:
void TForm1::DeleteAllImages()
{
for (int i = 0; i < c; i++)
{
delete Image[i];
Image[i] = NULL;
}
}
Create a a single image like this (you have to expand the parameters as you need them):
void TForm1::CreateImage(int nIndex, AnsiString str)
{
Image[nIndex] = new TImage(this);
/*Image[nIndex]->Parent = BoardItem ;
Image[nIndex]->Height = 20 ;
Image[nIndex]->Width = 20 ;
Image[nIndex]->Position->X = d ; // The programm asks you the coordinate at the begining of a new loop
Image[nIndex]->Position->Y = e ;
Image[nIndex]->Bitmap = Icon->Bitmap ;
Image[nIndex]->StyleName = str ;
Image[nIndex]->OnClick = ImageClick ;
*/
}
And in a loop you can create all images as you like:
void TForm1::CreateAllImages()
{
AnsiString str = " Test ";
for (int i = 0; i < c; i++)
{
// load data from anywhere...
CreateImage(i, str);
}
}
So, now you can operate in the Button-Event.
Delete all old Images, if existing.
Create all new Images.
void __fastcall TForm1::Button1Click(TObject *Sender)
{
// Delete old Images, if existing
if (CheckImagesLoaded())
{
DeleteAllImages();
}
// Create new Images
CreateAllImages();
}
Hope this helps...