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Example of `abstract factory' design pattern in C++
/*
* Example of `abstract factory' design pattern.
* Copyright (C) 2011 Radek Pazdera
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <iostream>
#include <string>
class Window
{
protected:
int width;
int height;
std::string toolkit;
std::string type;
Window(std::string usedToolkit, std::string windowType)
: toolkit(usedToolkit), type(windowType)
{}
public:
std::string getToolkit()
{
return toolkit;
}
std::string getType()
{
return type;
}
};
class GtkToolboxWindow : public Window
{
public:
GtkToolboxWindow()
: Window("Gtk", "ToolboxWindow")
{}
};
class GtkLayersWindow : public Window
{
public:
GtkLayersWindow()
: Window("Gtk", "LayersWindow")
{}
};
class GtkMainWindow : public Window
{
public:
GtkMainWindow()
: Window("Gtk", "MainWindow")
{}
};
class QtToolboxWindow : public Window
{
public:
QtToolboxWindow()
: Window("Qt", "ToolboxWindow")
{}
};
class QtLayersWindow : public Window
{
public:
QtLayersWindow()
: Window("Qt", "LayersWindow")
{}
};
class QtMainWindow : public Window
{
public:
QtMainWindow()
: Window("Qt", "MainWindow")
{}
};
/* This is the abstract factory. */
class UIFactory
{
public:
virtual Window* getToolboxWindow() = 0;
virtual Window* getLayersWindow() = 0;
virtual Window* getMainWindow() = 0;
};
/* Factory for Gtk toolkit */
class GtkUIFactory : public UIFactory
{
public:
Window* getToolboxWindow()
{
return new GtkToolboxWindow();
}
Window* getLayersWindow()
{
return new GtkLayersWindow();
}
Window* getMainWindow()
{
return new GtkMainWindow();
}
};
/* Factory for Qt toolkit */
class QtUIFactory : public UIFactory
{
public:
Window* getToolboxWindow()
{
return new QtToolboxWindow();
}
Window* getLayersWindow()
{
return new QtLayersWindow();
}
Window* getMainWindow()
{
return new QtMainWindow();
}
};
int main()
{
UIFactory* ui = 0;
/* Check what environment is running
and create appropriate factory. */
if (/* Gtk == */ true)
{
ui = new GtkUIFactory();
}
else
{
ui = new QtUIFactory();
}
/* Use the factory to build interface. */
Window* toolbox = ui->getToolboxWindow();
Window* layers = ui->getLayersWindow();
Window* main = ui->getMainWindow();
/* See what have we recieved. */
std::cout << toolbox->getToolkit() << ":"
<< toolbox->getType() << std::endl;
std::cout << layers->getToolkit() << ":"
<< layers->getType() << std::endl;
std::cout << main->getToolkit() << ":"
<< main->getType() << std::endl;
}

Nice example!

After Window* toolbox = ui->getToolboxWindow(); line
It calls return new QtToolboxWindow(); line.
It allocate memory and return which store in toolbox pointer in main function.
How can I delete this and who is responsible for deallocate the memory.
what is the delete procedure.
Is it create the memory leakage issue???

@erfanhossainshoaib : It looks like leaks to me. One way to solve this is to store these pointers in RAII auto pointers like this : std::unique_ptr<Window> toolbox(ui->getToolboxWindow(););

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