Ruby class expects class variable but only in Rake task - ruby

Question

I am trying to seed my database with some dummy data, so I have this seed file:
db/seeds.rb
require 'require_all'
require_all 'lib'
Author.create(name: "Mark Twain")
My Ruby model and relevant methods:
lib/author.rb
class Author
attr_accessor :name, :id
def initialize(name, id=nil)
#name = name
#id = id
end
def self.make_object_from_row(row)
# [1, "Mark Twain"]
Author.new(row[1], row[0])
end
def self.create(name)
author = Author.new(name)
author.save
end
def save
if self.id.nil? # doesn't exist in the database yet
sql = <<-SQL
INSERT INTO authors (name)
VALUES (?)
SQL
DB.execute(sql, self.name)
sql = "SELECT last_insert_rowid()"
self.id = DB.execute(sql)[0][0]
else # just update the row in the db
sql = <<-SQL
UPDATE authors SET (name) = ? WHERE id = ?
SQL
DB.execute(sql, self.name, self.id)
end
end
Rakefile
require_relative './config/environment'
desc "Set up database"
task :db_setup do
author_sql = <<-SQL
CREATE TABLE IF NOT EXISTS authors(
id integer PRIMARY KEY,
name varchar(255)
);
SQL
DB.execute(author_sql)
end
desc "Seed database"
task :db_seed do
ruby "db/seeds.rb"
end
config/environment.rb
require 'bundler/setup'
Bundler.require
# setting up the database connection (old way)
DB = SQLite3::Database.new("db/development.db")
require_relative '../lib/author.rb'
When I run the rake task for db_seed I get the error . lib/author.rb:26:in save': uninitialized constant Author::DB (NameError)
The db_setup Rake task works fine. Also if I go into a pry from my console, I can instantiate a new Author without a problem (and it writes to the database). If I run the seed file from my command line, I get the same error.
I see that it's looking for an attribute DB on the Author class, but I don't see why, or why it's inconsistent in that I can create an Author from the command line but not from the Rake task--if the variable were undefined that shouldn't make a difference, correct?
(I'm also aware that using ActiveRecord would be much easier, but I'm not looking to use it right now)

Answer 1

When you see errors like "uninitialized constant" popping up and you're sure you've defined that constant in a file somewhere, make sure you're loading that code in before the method with the error runs.
It looks like in this case config/environment wasn't loaded before DB was referenced, so it can't complete.
Due to how Ruby searches for constants it's presented as Author::DB because the code was running inside of the Author namespace and that's where searches start.