c1505 / ruby-puppy-v-000

Ruby Remembrance Lab

Objectives

1. Use a class variable to keep track of every instance of a class that is created.
2. Write a class method to access the list of all instances of a class, stored in a class variable.

Overview

The government has decided to start tracking every new puppy that is born, just like we track every new child who is born with a birth certificate. Because you're such a notoriously skilled programmer, you've been hired by the newly minted United States Department of Canines to write a program that will do just that.

You need to write a program that stores each new puppy that is born. You will write a Dog class that initializes with a name and also stores each new instance of Dog that is instantiated.

Instructions

Code your solution in lib/dog.rb

This lab is primarily test-driven. Run the test suite with the learn command and follow the test output to get started.

Some guidelines:

• You'll need to set a class variable equal to an empty array inside your class. Call your class variable @@all.
• This array is the storage container for each instance of a Dog that gets created. In other words, every puppy that is born should get pushed into this array at the moment of instantiation––in the #initialize method! Use the self keyword inside the #initialize method to refer to the new dog you are trying to store in your @@all array.
• You will need to write a class method, .all, that iterates over all of the individual dogs stored in the @@all array and puts out their name to the terminal.

There is one method that we'll talk about together:

The .clear_all Method

What happens if we want to clear out our list of existing dogs? It is not at all uncommon to want to "reset" or "restart" our program. You'll be building a class method, .clear_all, that does just that. This method should operate on the @@all array of existing dogs and empty that array. Hint: look up the Array#clear method.

A Note on Testing

In the test suite, you'll see this code:

expect(Dog.class_variable_get(:@@all)).to match([])

Here, we are using the .class_variable_get(name_of_class_variable) method on the Dog class. This method introspects on the class on which it is called and retrieves the value of the class variable passed into the method as an argument. We use it here in the test suite to check that you do in fact set a class variable, @@all, equal to an empty array and that you fill that array up with new dogs as they are instantiated.