polymorphism

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:
 

cpp/Polymorphism.md

@@ -0,0 +1,5 @@
+# Polymorphism
+
+Relevant files:
+
+- [main.cpp](./inheritance/main.cpp)

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)
 

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);
 };

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;
 }

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;
 };

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;
 }

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;
 };

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();
 }