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Plays-Playwrights ORM

In tonight's videos, we saw how to implement an ORM for the plays database. Your homework is to expand this ORM!

Setup

Let's start with the code from the video lectures. Download the skeleton here.

Next, let's create our database. In SQLite, our databases are just files that store all our data. They are updated by executing SQL commands (creating/updating tables and rows). Our import_db.sql has all the code to create our tables and some seed data. We can create our database with the following command:

cat import_db.sql | sqlite3 plays.db

This will apply all the SQL commands in import_db.sql to plays.db from the sqlite3 console. You should now see a plays.db file in your project directory. Let's get started.

Enhancing Functionality

Let's add the following methods to our ORM:

  • Play::find_by_title(title)
  • Play::find_by_playwright(name) (returns all plays written by playwright)

In addition, create a Playwright class and add the following methods to our ORM.

  • Playwright::all
  • Playwright::find_by_name(name)
  • Playwright#new (this is the initialize method)
  • Playwright#create
  • Playwright#update
  • Playwright#get_plays (returns all plays written by playwright)

Remember, our PlayDBConnection class accesses the database stored in plays.db, which includes both the plays and playwrights tables.

Testing your ORM

  • Open up pry and load the plays.rb file
  • Initialize an instance of the Playwright class by calling Playwright#new and passing it the necessary arguments.
    • Call Playwright#create on the instance that you just initialized. Then call Playwright::all to see that it was added to the database correctly.
  • Similarly, test Playwright#update and Playwright#get_plays by calling them on instances of the Playwright class.

For a more detailed look at how to test your ORM, refer to the ORM Demo (jump to 18m25s).