From 0d55cf12734453cc35753b81a003e15c52da3457 Mon Sep 17 00:00:00 2001
From: Timo Hocker <t-hocker@web.de>
Date: Sun, 24 May 2020 17:39:59 +0200
Subject: [PATCH] polymorphism

---
 README.md                 |  6 +++---
 cpp/Polymorphism.md       |  5 +++++
 cpp/inheritance/README.md |  2 --
 cpp/inheritance/animal.h  |  1 +
 cpp/inheritance/cat.cpp   |  3 +++
 cpp/inheritance/cat.h     |  3 +++
 cpp/inheritance/dog.cpp   |  1 +
 cpp/inheritance/dog.h     |  3 +++
 cpp/inheritance/main.cpp  | 13 +++++++++----
 9 files changed, 28 insertions(+), 9 deletions(-)
 create mode 100644 cpp/Polymorphism.md

diff --git a/README.md b/README.md
index f5c983e..c915dd7 100644
--- a/README.md
+++ b/README.md
@@ -15,9 +15,9 @@ Lessons:
 - [creating a class](./lessons/Classes.md)
 - [constructors](./lessons/Constructors.md)
 - [encapsulation](./lessons/Encapsulation.md)
-- [inheritance](./lessons/Inheritance.md) <--
-- [properties](./lessons/Properties.md)
-- [polymorphism](./lessons/Polymorphism.md)
+- [inheritance](./lessons/Inheritance.md)
+- [properties](./lessons/Properties.md) -
+- [polymorphism](./lessons/Polymorphism.md) -
 
 Work in progress:
 
diff --git a/cpp/Polymorphism.md b/cpp/Polymorphism.md
new file mode 100644
index 0000000..ca0e969
--- /dev/null
+++ b/cpp/Polymorphism.md
@@ -0,0 +1,5 @@
+# Polymorphism
+
+Relevant files:
+
+- [main.cpp](./inheritance/main.cpp)
diff --git a/cpp/inheritance/README.md b/cpp/inheritance/README.md
index 62d54a2..70ff893 100644
--- a/cpp/inheritance/README.md
+++ b/cpp/inheritance/README.md
@@ -5,8 +5,6 @@ little to complicated for this lesson.
 
 Relevant files:
 
-- [main.cpp](./index.cpp)
-
 - [animal.h](./animal.h)
 - [animal.cpp](./animal.cpp)
 
diff --git a/cpp/inheritance/animal.h b/cpp/inheritance/animal.h
index df2c12f..15b981f 100644
--- a/cpp/inheritance/animal.h
+++ b/cpp/inheritance/animal.h
@@ -7,6 +7,7 @@ class animal
 {
   public:
     std::string name;
+    // define make_sound as virtual to allow overriding in subclasses
     virtual void make_sound();
     animal(std::string name);
 };
diff --git a/cpp/inheritance/cat.cpp b/cpp/inheritance/cat.cpp
index f5295a4..9bbf579 100644
--- a/cpp/inheritance/cat.cpp
+++ b/cpp/inheritance/cat.cpp
@@ -4,6 +4,9 @@
 #include <string>
 
 void cat::make_sound() {
+  // call the base class function first
   animal::make_sound();
+
+  // add additional functionality
   cout << "meow" << endl;
 }
diff --git a/cpp/inheritance/cat.h b/cpp/inheritance/cat.h
index 142e8f9..79e2098 100644
--- a/cpp/inheritance/cat.h
+++ b/cpp/inheritance/cat.h
@@ -1,12 +1,15 @@
 #pragma once
 
 #include <string>
+// include the animal header
 #include "animal.h"
 using namespace std;
 
 class cat: public animal
 {
+  // include the animal constructor
   using animal::animal;
   public:
+    // override the make_sound function
     void make_sound() override;
 };
diff --git a/cpp/inheritance/dog.cpp b/cpp/inheritance/dog.cpp
index f6eb9c4..2e04487 100644
--- a/cpp/inheritance/dog.cpp
+++ b/cpp/inheritance/dog.cpp
@@ -4,6 +4,7 @@
 #include <string>
 
 void dog::make_sound() {
+  // implement own functionality
   cout << "doggo " << name << " says:" << endl;
   cout << "woof!" << endl;
 }
diff --git a/cpp/inheritance/dog.h b/cpp/inheritance/dog.h
index c771d7e..4a533b1 100644
--- a/cpp/inheritance/dog.h
+++ b/cpp/inheritance/dog.h
@@ -1,12 +1,15 @@
 #pragma once
 
 #include <string>
+// include the animal header
 #include "animal.h"
 using namespace std;
 
 class dog: public animal
 {
+  // include the animal constructor
   using animal::animal;
   public:
+    // override the make_sound function
     void make_sound() override;
 };
diff --git a/cpp/inheritance/main.cpp b/cpp/inheritance/main.cpp
index 03ffd1d..073a85a 100644
--- a/cpp/inheritance/main.cpp
+++ b/cpp/inheritance/main.cpp
@@ -1,12 +1,17 @@
+#include "animal.h"
 #include "cat.h"
 #include "dog.h"
 
 #include <string>
 
 int main() {
-  dog d("buster");
-  cat c("mittens");
+  // because cat and dog are subclasses of animal, they can be stored in an array of animals
+  animal * animals[2] = {
+    new dog("buster"),
+    new cat("mittens")
+  };
 
-  d.make_sound();
-  c.make_sound();
+  for (animal * a : animals)
+    // when calling the make_sound function, the implementation of the actual class gets called (in this case cat or dog)
+    a->make_sound();
 }