Changes needed to follow examples in old versions of Agile Web Development with Rails

I've been reading Agile Web Development with Rails, version 2005-9-13. The Ruby on Rails framework has been updated since this release. This page lists some of the errata that I came across and describes what changes to make so that you can follow the code examples.

A full comprehensive list can be found on the Pragmatic Programmer's web site: Errata for Agile Web Development with Rails - First Edition

Change MySQL tables from MyISAM to InnoDB

The SQL in the book is for MyISAM tables. The default config for the (Ruby on) Rails test framework sets use_transactional_fixtures = true in the test/test_helper.rb file, which means that transactional support is needed in order for the test fixtures to work. You could presumably change the variable to false, or you could change your database to one that supports transactions. For MySQL, this means you need InnoDB tables.

To convert the MyISAM tables to InnoDB, you have to

1. Edit the SQL so that the foreign keys are indexed
2. Make sure that any tables containing a referenced column are created before the tables which defines the foreign keys

So, the InnoDB SQL I used was as follows:

drop table if exists products;
create table products (
  id          int           not null auto_increment,
  title       varchar(100)  not null,
  description text          not null,
  image_url   varchar(100)  not null,
  price       decimal(10,2) not null,
  date_available datetime   not null,
  primary key (id)
)type=innodb;

drop table if exists orders;
create table orders (
  id         int          not null auto_increment,
  name       varchar(100) not null,
  email      varchar(255) not null,
  address    text         not null,
  pay_type   char(10)     not null,
  shipped_at datetime     null,
  primary key (id)
)type=innodb;

drop table if exists line_items;
create table line_items (
  id             int           not null auto_increment,
  product_id	 int	       not null,
  order_id	 int	       not null,
  quantity	 int           not null default 0,
  unit_price	 decimal(10,2) not null,
  index (product_id),
  index (order_id),
  constraint fk_items_product  foreign key (product_id) references products(id),
  constraint fk_items_order    foreign key (order_id) references orders(id),
  primary key (id)
)type=innodb;

drop table if exists users;
create table users (
  id              int          not null auto_increment,
  name            varchar(100) not null,
  hashed_password char(40)     null,
  primary key (id)
)type=innodb;

For more details and the other requirements of InnoDB tables, see the 14.2.7.4. FOREIGN KEY Constraints page the MySQL 3.23, 4.0, 4.1 Reference Manual.

Fix for nil object error in Rails test fixtures

The following was copied from Fix for nil object error in Rails test fixtures from the CodeSnippets repository.

# NoMethodError: You have a nil object when you didn't expect it!

self.use_instantiated_fixtures = true

Last modified: 17/04/2007 Tags: (none)