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C++ London Uni Week 14 Inheritance Exercise

Congratulations! You have been appointed as Chief Technology Officer for CatBook, a new social media start-up which allows users to post pictures of their cats.

Task 1

A user's news feed consists of cat pictures. There are two types of pictures that CatBook supports: cute cats and grumpy cats.

  1. Write an abstract base class CatPicture with a pure virtual member function std::string get_description() const.

  2. Write a class CuteCatPicture which inherits from CatPicture. Its constructor should take an argument which is a std::string of the cat's name. It should implement get_description(), returning the string

    A picture of <cat name> looking adorably cute

    where <cat name> was the name provided to the CuteCatPicture constructor.

  3. Write another similar class GrumpyCatPicture which again inherits from CatPicture, and again allows you to pass the cat name to its constructor. This time, the implementation of get_description() should return

    A picture of <cat name> looking really grumpy

Task 2

Hooray, CatBook is starting to attract users! It's time to take this opportunity to improve your code. The CuteCatPicture and GrumpyCatPicture subclasses do very similar things: you can move some of this common code into the CatPicture base class.

  1. Add a constructor to the CatPicture base class which takes a std::string and stores it in a field named cat_name. Add a member function get_cat_name() which only derived classes may call.

  2. Refactor your CuteCatPicture and GrumpyCatPicture subclasses to call the new base class constructor. Use the new get_cat_name() function in each implementation of get_description().

  3. Everybody likes cat pictures. Add a new member function like() which, when called, increments the like_count of a picture. Add a member function get_num_likes() which returns a picture's current like_count.

Task 3

Oh no, your investor funding has run out! CatBook needs to make money, fast.

We need to remodel the code so that body CatPictures and Adverts can be displayed in the news feed.

  1. Add a new abstract base class NewsItem which represents an item in the news feed. This class should have a get_item_text() pure virtual member function.

  2. Make CatPicture inherit from NewsItem, and implement get_item_text() appropriately.

  3. Write an Advert class which takes a std::string slogan in its constructor. Implement the get_item_text() function so that it returns the slogan.