Solution

exercise/01/animal.cpp

@@ -0,0 +1,63 @@
+#include "animal.h"
+#include <exception>
+
+animal::~animal() { }
+
+const std::wstring cockroach::type = L"cockroach";
+
+std::wstring cockroach::species() const
+{
+	return type;
+}
+
+unsigned int insect::legs() const
+{
+	return number_of_legs;
+}
+
+const std::wstring sparrow::type = L"sparrow";
+
+std::wstring sparrow::species() const
+{
+	return type;
+}
+
+unsigned int bird::legs() const
+{
+	return number_of_legs;
+}
+
+const std::wstring tarantula::type = L"tarantula";
+
+std::wstring tarantula::species() const
+{
+	return type;
+}
+
+unsigned int spider::legs() const
+{
+	return number_of_legs;
+}
+
+std::wstring leg_counter::add_animal(const animal_factory & factory)
+{
+	std::unique_ptr<animal> animal = factory.create_animal();
+	number_of_legs += animal->legs();
+	return animal->species();
+}
+
+unsigned int leg_counter::legs() const
+{
+	return number_of_legs;
+}
+
+std::unique_ptr<animal> animal_factory::create_animal() const
+{
+	switch (animal_num)
+	{
+	case 1: return std::make_unique<cockroach>();
+	case 2: return std::make_unique<sparrow>();
+	case 3: return std::make_unique<tarantula>();
+	}
+	throw std::invalid_argument("There is no animal with that number!");
+}

exercise/01/animal.h

@@ -0,0 +1,84 @@
+#pragma once
+#include <string>
+
+class animal
+{
+public:
+	virtual std::wstring species() const = 0;
+	virtual unsigned int legs() const = 0;
+	virtual ~animal() = 0;
+};
+
+class insect : public animal
+{
+public:
+	~insect() {};
+	unsigned int legs() const override;
+private:
+	static const unsigned int number_of_legs = 6;
+};
+
+class bird : public animal
+{
+public:
+	~bird() {};
+	unsigned int legs() const override;
+private:
+	static const unsigned int number_of_legs = 2;
+};
+
+class spider : public  animal
+{
+public:
+	~spider() {};
+	unsigned int legs() const override;
+private:
+	static const unsigned int number_of_legs = 8;
+};
+
+class cockroach : public insect
+{
+public:
+	~cockroach() {};
+	std::wstring species() const override;
+private:
+	static const std::wstring type;
+};
+
+class sparrow : public bird
+{
+public:
+	~sparrow() {};
+	std::wstring species() const override;
+private:
+	static const std::wstring type;
+};
+
+class tarantula : public spider
+{
+public:
+	~tarantula() {};
+	std::wstring species() const override;
+private:
+	static const std::wstring type;
+};
+
+class animal_factory
+{
+public:
+	animal_factory(unsigned int animal_num) : animal_num(animal_num) {};
+	std::unique_ptr<animal> create_animal() const;
+
+private:
+	unsigned int animal_num;
+};
+
+class leg_counter
+{
+public:
+	std::wstring add_animal(const animal_factory& factory);
+	unsigned int legs() const;
+
+private:
+	unsigned int number_of_legs = 0;
+};