project: Animals Part 1. OOP basics

Story points 3
Tags oop skill/oop
Hard Prerequisites
IMPORTANT: Please review these prerequisites, they include important information that will help you with this content.
  • PROJECTS: Person

    • Project structure

    JavaScript

    Your directory structure should look like this:

    ├── src
|   └── animals.js
└── package.json

    Note: You will be asked to create a number of classes. Make sure you export them using the following syntax:

    module.exports = {class1Name, class2Name, ...}

    Note: Your package.json should be valid. If it is a blank file then your project will not be marked as competent. If you are not sure what a valid package.json should look like, then look it up!

    Python

    Your directory structure should look like this:

    ├── animals
│   └── animals.py
├── setup.py

    Java

    Please make use of Gradle from the command line to set up your project. You can learn more about Gradle here:

    [TODO] TOPIC: African Coding Network Syllabus

    When you use gradle to create your project, give your project the following name: animals

    Your directory structure should look like this:

    ├── app
|   ├── build.gradle
|   └── src
|       └── main
|           └── java
|               └── animals
|                   └── Animals.java <-------- names are important
|                   └── Cat.java <-------- names are important
|                   └── Dog.java <-------- names are important
|                   └── Home.java <-------- names are important
├── gradle
│   └── wrapper
│       ├── gradle-wrapper.jar
│       └── gradle-wrapper.properties
├── gradlew
├── gradlew.bat
└── settings.gradle
...

    Make sure that all of the classes you define are within the animals package. Do this by including a package declaration at the top of each of your java files.

    Instructions

    In this challenge, you will create 3 classes.

    1. Super class called Animal
    2. Dog and Cat class both extend Animal class (a dog is an animal, and a cat is an animal).
    3. Dog and Cat class should only have one function, which is their own implementation of the sound() function. This is polymorphism.

    Animal Flow Diagram

    // Java

? dog1 = new Dog()  
? dog2 = new Dog("Simba")

dog1.eat()   // public returns 'Rax eats'
dog1.sound() // returns 'Bark'

dog2.eat()   // returns 'Simba eats'
dog2.sound() // returns 'Bark'

? cat1 = new Cat()
? cat2 = new Cat("Smokey")

cat1.eat()   // returns 'Stormy eats'
cat1.sound() // returns 'Meow'

cat2.eat()   // returns 'Smokey eats'
cat2.sound() // returns 'Meow'

// Make sure all constructors, eat and sound are all public methods

    // JavaScript

let dog1 = new Dog();
let dog2 = new Dog("Simba")

dog1.eat();   // returns 'Rax eats'
dog1.sound(); // returns 'Bark'

dog2.eat()   // returns 'Simba eats'
dog2.sound() // returns 'Bark'

let cat1 = new Cat();
let cat2 = new Cat("Smokey")

cat1.eat();   // returns 'Stormy eats'
cat1.sound(); // returns 'Meow'

cat2.eat()    // returns 'Smokey eats'
cat2.sound()  // returns 'Meow'

    
# Python

dog1 = Dog()
dog2 = Dog('Simba')

dog1.eat()   # returns 'Rax eats'
dog1.sound() # returns 'Bark'

dog2.eat()   # returns 'Simba eats'
dog2.sound() # returns 'Bark'

cat1 = Cat()
cat2 = Cat('Smokey')

cat1.eat()   # returns 'Stormy eats'
cat1.sound() # returns 'Meow'

cat2.eat()   # returns 'Smokey eats'
cat2.sound() # returns 'Meow'
    1. Now let’s add composition. Make a new class called Home. Lots of people have dogs and cats in their homes. Home should have a function called adopt pet that takes any Animal as an input and returns the number of pets that have been adopted thus far. The new pet should be stored in the Home object in an array/list. The Home object should also have a function called make all sounds. It should work like this:
    // Java

Home home = new Home()
? dog1 = new Dog()
? dog2 = new Dog()
? cat = new Cat()

home.makeAllSounds() // this returns an empty ArrayList
home.adoptPet(dog1) // 1
home.makeAllSounds()
// this returns an ArrayList of Strings:
// ["Bark"]

home.adoptPet(cat) // 2
home.makeAllSounds()
// this returns an ArrayList of Strings:
// ["Bark", "Meow"]

home.adoptPet(dog2) // 3
home.makeAllSounds()
// this returns an ArrayList of Strings:
// ["Bark", "Meow", "Bark"]

// adoptPet and makeAllSounds must be public methods

    // JavaScript

let home = new Home();
let dog1 = new Dog();
let dog2 = new Dog();
let cat = new Cat();


home.makeAllSounds();// this returns an empty array
home.adoptPet(dog1); // 1
home.makeAllSounds();
// this returns:
// ["Bark"]

home.adoptPet(cat); // 2
home.makeAllSounds();
// this returns:
// ["Bark", "Meow"]

home.adoptPet(dog2); // 3
home.makeAllSounds();
// this returns:
// ["Bark", "Meow", "Bark"]

    # Python

home = Home()
dog1 = Dog()
dog2 = Dog()
cat = Cat()

home.make_all_sounds() // this returns an empty ArrListay
home.adopt_pet(dog1) # 1
home.make_all_sounds()
# this returns:
# ["Bark"]


home.adopt_pet(cat) # 2
home.make_all_sounds()
# this returns:
# ["Bark", "Meow"]

home.adopt_pet(dog2) # 3
home.make_all_sounds
# this returns:
# ["Bark", "Meow", "Bark"]

    Add some functionality to adopt pet so that an error/exception, gets raised/thrown if you try to adopt the same pet twice. Make sure that the error has a useful message!

    For example,

    home.adoptPet(dog1) // returns the number of pets that have been adopted thus far
home.adoptPet(dog1) // an error/exception gets raised

    Check your understanding

    Consider the following OOP concepts. Can you see and explain how they are demonstrated in this project?

    1. Encapsulation
    2. Inheritance
    3. Polymorphism
    4. Composition

    Instructions for reviewer

    • The Animal class should follow the document’s diagram’s instructions exactly.
    • A constructor that accepts a string to set the name for the constructed pet should exist.
    • The makeAllSounds method should return an array of the exact strings specified in the instructions. e.g “Bark”, “Meow”
    • All the class methods should return the exact strings defined and not print them.
    • A house cannot adopt a specific instance of a pet more than once.
    • Make sure any error messages are descriptive
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