1 files changed, 121 insertions, 0 deletions
diff --git a/src/lesson21_oop_inherit.cpp b/src/lesson21_oop_inherit.cpp
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+++ b/src/lesson21_oop_inherit.cpp
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+//============================================================================
+// Author      : Sven Göthel
+// Copyright   : 2024 Göthel Software e.K.
+// License     : MIT
+// Description : C++ Lesson 2.1 OOP (simple class inheritance w/o virtual functions)
+//============================================================================
+
+#include <limits>
+#include <string>
+#include <memory>
+#include <cassert>
+#include <iostream>
+
+class creature_t {
+    protected:
+        typedef std::string (*to_string_func_t)(const creature_t&) noexcept;
+
+    private:
+        to_string_func_t m_to_string;
+        int m_init_lifetime_left;
+        int m_lifetime_left;
+
+    protected:
+        /** Custom constructor (ctor) */
+        creature_t(to_string_func_t to_string_func, int lifetime_left) noexcept
+        : m_to_string(to_string_func),
+          m_init_lifetime_left(lifetime_left),
+          m_lifetime_left(lifetime_left) {}
+
+        /** Copy ctor */
+        creature_t(const creature_t& o) noexcept = default;
+
+    public:
+        /** Destructor (dtor) */
+        ~creature_t() noexcept = default;
+
+        int total_lifetime() const noexcept { return m_init_lifetime_left; }
+        int lifetime_left() const noexcept { return m_lifetime_left; }
+        int age() const noexcept { return total_lifetime() - lifetime_left(); }
+        bool alive() const noexcept { return lifetime_left() > 0; }
+        std::string lifesign() const noexcept { return alive() ? "☀" : "✝"; }
+
+        /** Subtract given years of life and return whether there is lifetime left */
+        bool tick(int years) noexcept {
+            if( m_lifetime_left > years ) {
+                m_lifetime_left -= years;
+                return true;
+            } else {
+                m_lifetime_left = 0;
+                return false;
+            }
+        }
+
+        std::string to_substring() const noexcept {
+            return "age "+std::to_string(age())+"/"+std::to_string(total_lifetime());
+        }
+
+        std::string to_string() const noexcept {
+            return m_to_string(*this);
+        }
+};
+
+std::ostream& operator<<(std::ostream& out, const creature_t& v) {
+    return out << v.to_string();
+}
+
+class plant_t : public creature_t {
+    public:
+        /** Custom constructor (ctor) */
+        plant_t(int lifetime_left) noexcept
+        : creature_t(to_string_impl, lifetime_left) {}
+
+        /** Copy ctor */
+        plant_t(const plant_t& o) noexcept
+        : creature_t(o) { }
+
+    private:
+        static std::string to_string_impl(const creature_t& t) noexcept {
+            return "plant"+t.lifesign()+"["+t.to_substring()+"]";
+        }
+};
+
+class animal_t : public creature_t {
+    public:
+        /** Custom constructor (ctor) */
+        animal_t(int lifetime_left) noexcept
+        : creature_t(to_string_impl, lifetime_left) {}
+
+        /** Copy ctor */
+        animal_t(const creature_t& o) noexcept
+        : creature_t(o) { }
+
+    private:
+        static std::string to_string_impl(const creature_t& t) noexcept {
+            return "animal"+t.lifesign()+"["+t.to_substring()+"]";
+        }
+};
+
+int main(int, char*[]) {
+    plant_t p1(3);
+    animal_t a1(80);
+
+    std::cout << "00.p1 = " << p1 << std::endl;
+    std::cout << "00.a1 = " << a1 << std::endl;
+
+    creature_t& c1p1 = p1, &c2a1 = a1;
+    std::cout << "00.c1p1 = " << c1p1 << std::endl;
+    std::cout << "00.c2a1 = " << c2a1 << std::endl;
+
+    p1.tick(1);
+    a1.tick(1);
+    std::cout << "01.p1 = " << p1 << std::endl;
+    std::cout << "01.a1 = " << a1 << std::endl;
+
+    p1.tick(2);
+    a1.tick(79);
+    std::cout << "03.p1 = " << p1 << std::endl;
+    std::cout << "79.a1 = " << a1 << std::endl;
+
+    return 0;
+}