Dynamic alocation an array of Images in C++ Builder

问题

I want to make a game of BlackJack.

I want to make a vector of images and when I press a button a new image shows up(need 2 or 3 images).

After that I want to delete all of them in another button press.

I try to declare an vector in main class(Unit1.h):

class TForm1 : public TForm{

...

public: TImage* Images[];

And in Form1(Unit1.cpp):

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    //  i=1 is global 
    Images[i] =new TImage(this);
    Images[i]->Parent=this;
    Images[i]->Picture->Bitmap->...//here i want to use it 
    i++;
}

And here i want to delete them:

void __fastcall TForm1::Button3Click(TObject *Sender)
{
    for(int k=1;k<=i;i++) {
        Images[k]->~TImage();   //delete Images[k];
    }
}

回答1:

You did not declare a vector. std::vector is an actual class type in C++. What you actually declared is a static array of unknown size. You cannot do that. You must specify a constant for the size at compile-time, eg:

class TForm1 : public TForm
{
...
public:
    TImage* Images[3];
};

If you do not know the number of images at compile-time, you must declare a pointer to an array that is dynamically allocated at runtime instead:

class TForm1 : public TForm
{
...
public:
    TImage** Images;
    int TotalNumberOfImages;
    int NumberOfImages;

    __fastcall TForm1(TComponent *Owner);
    __fastcall ~TForm1();
};

__fastcall TForm1::TForm1(TComponent *Owner)
: TForm(Owner)
{
    TotalNumberOfImages = ...;
    Images = new TImage*[TotalNumberOfImages];
    NumberOfImages = 0;
}
__fastcall TForm1::~TForm1()
{
    delete[] Images;
}

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    if (NumberOfImages < TotalNumberOfImage)
    {
        TImage *img = new TImage(this);
        img->Parent = this;
        img->Picture->...
        ...
        Images[NumberOfImages++] = img;
    }
}

void __fastcall TForm1::Button3Click(TObject *Sender)
{
    for(int k = 0; k < NumberOfImages; ++k)
        delete Images[k];
    NumberOfImages = 0;
}

If you really want to use a std::vector, it should be more like this instead:

#include <vector>

class TForm1 : public TForm
{
...
public:
    std::vector<TImage*> Images;
};

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TImage *img = new TImage(this);
    img->Parent = this;
    img->Picture->...
    ...
    Images.push_back(img);
}

void __fastcall TForm1::Button3Click(TObject *Sender)
{
    for(int k = 0; k < Images.size(); ++k)
        delete Images[k];
    /*
    or:
    for(std::vector<TImage*>::iterator iter = Images.begin(), end = Images.end(); iter != end; ++iter)
        delete *iter;
    */

    Images.clear();
}

Or, if you are using one of Embarcadero's Clang-based C++11 compilers:

#include <vector>
#include <memory>

class TForm1 : public TForm
{
...
public:
    std::vector<std::unique_ptr<TImage*>> Images;
};

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    std::unique_ptr<TImage> img(new TImage(this));
    img->Parent = this;
    img->Picture->...
    ...
    Images.push_back(img);
}

void __fastcall TForm1::Button3Click(TObject *Sender)
{
    Images.clear();
}

来源：https://stackoverflow.com/questions/34141850/dynamic-alocation-an-array-of-images-in-c-builder

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c++

c++builder