class GraphicsView : public QGraphicsView
  class mySquare : public QObject, public QGraphicsRectItem
  class Scene : public QGraphicsScene 

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void mySquare::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
      QRectF rect(0,0,_width,_height);
      painter->drawRect(rect);
}

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 void GraphicsView::wheelEvent(QWheelEvent * event)
{
    int angle = event->angleDelta().y(); // angle will tell you zoom in or out.
    double scaleFactor = 1.15; //How fast we zoom
    setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
    if (angle > 0)
    {
        qDebug()<<"Zoom in";
        scale(scaleFactor, scaleFactor);
    }
    else
    {
        qDebug()<<"Zoom out";
        scale(1.0 / scaleFactor, 1.0 / scaleFactor);
    }
        mySquare  _square = new mySquare(0,blankImage);
       _square->setPos(QPointF(0, 0));
       //add square to scene. 
] //Bug!!! Why after scale function call, _square failed to draw rect in paint method.
]        _scene->addItem(_square);
        _square->update(); 
}

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template<typename A, typename B>
class BaseFunc
{
public:
	virtual B Call(A in1)
	{
		B b;
		return b;
	}
};

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class AnimalName :
	public BaseFunc<Animal, std::string>
{
public:
	virtual std::string Call(
		const std::shared_ptr<Animal> &customer);
};

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class Animal
{
public:
	static std::vector<Animal> animals;
	int id = 0;
	std::string name = "";

	Animal();

	static std::vector<std::string> GetAnimalNames();

	template<typename T>
	static std::vector<T> GetAnimalByFunction(
		const std::shared_ptr<BaseFunc<Animal, T>> &funct);
};

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#include "Animal.h"

using namespace std;

vector<Animal> Animal::animals;

Animal::Animal()
{
}

string AnimalName::Call(
	const shared_ptr<Animal> &animal)
{
	return animal->name;
}

vector<string> Animal::GetAnimalNames()
{
	return Animal::GetAnimalByFunction<string>(
		make_shared<AnimalName>());
}

template<typename T>
vector<T> Animal::GetAnimalByFunction(
	const shared_ptr<BaseFunc<Animal, T>> &funct)
{
	vector<T> returnList;
	for (auto customer : Animal::animals)
	{
		returnList.push_back(
			funct->Call(customer));
	}
	return returnList;
}

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#include <iostream>
#include "Animal.h"

using namespace std;

void SetAnimals()
{
	int i = 0;

	vector<string> animalNames;
	animalNames = {
		"Peanut",
		"Coco",
		"Rocky",
		"Harley",
		"Pepper",
		"Roxy"
	};

	for (auto name : animalNames)
	{
		Animal a;
		a.id = i++;
		a.name = name;
		Animal::animals.push_back(a);
	}
}

int main()
{
	Animal a;

	SetAnimals();

	cout << "Animal names:" << endl;
	vector<string> animals =
		a.GetAnimalNames();
	for (auto name : animals)
	{
		cout << name << endl;
	}

	return 0;
}

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