Ruby Database Connectivity

After mostly doing RoR work for the last several months, lately I've had to write a few command line scripts that interact with MySQL.

I came across an article by Steve Litt on Troubleshooters.com, which I found useful for comparing the mysql driver, dbi, and ActiveRecord:

Ruby Database Connectivity

And here a few articles by Paul DuBois on Ruby and database connectivity:

Using the Ruby MySQL Module

Using the Ruby DBI Module

Ruby on Rails - Legacy MySQL Database

I'm rewriting a company admin tool written in mod_perl (Catalyst) and replacing it with a new one using Ruby on Rails. At the moment, I have to keep the legacy database/schema. Most of the old tables don't use auto-incrementing keys, which means I won't get the Rails Active::Record magic and I need to work around the keys.

Here's an example table:

mysql> describe clients;
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| client_abbrv | varchar(5) | NO | PRI | | |
| client_name | varchar(50) | YES | | NULL | |
+--------------+-------------+------+-----+---------+-------+

To get this to work with Rails, I had to make a few small changes.

I made one small change in the view, which was setting the name of the primary key field. I changed "client_abbrv" to "id" in the form:

app/views/client/new.rhtml

<%= error_messages_for 'client' %>

  <fieldset>
    <legend>Add a Client
    <% form_tag :action => "create" do %>
      <p>
        <label for="client_client_name">Client Name:
        <%= text_field 'client', 'client_name'  %>
      </p>
      <p>
        <label for="client_id">Client Abbrv:
        <%= text_field 'client', 'id' %>
      </p>
      <p>
      <%= submit_tag 'Add' %>
      </p>
    <% end %>
  </fieldset>

For the model, I had set the primary key with set_primary_key.

app/models/clients.rb

class Client < ActiveRecord::Base
set_primary_key "client_abbrv"
end

Luckily, the table was already pluralized. If it had been "client," then I would have had to add this line:

def self.table_name() "client" end

For the controller, I had to change the create method:

app/controllers/client_controller.rb

def create
  @client = Client.new
  @client.id = params[:client][:id]
  @client.client_name = params[:client][:client_name]
  if @client.save
    flash[:notice] = "Client was successfully created."
    redirect_to :action => 'list'
  else
    render :action => 'new'
  end
end

That replaced the old create method where I had the normal:

@client = Client.new(params[:client])

When using set_primary_key, you insert data using "id" and typically select data using the actual field name, "client_abbrv" in this case.

Here's what the controller is doing for the create method:

dsparling-imbps-computer:~/my/rubydev/uclick-admin dsparlingimbp$ script/console 
Loading development environment.
>> client = Client.new
=> #<Client:0x32b5e14 @new_record=true, @attributes={"client_name"=>nil}>
>> client.id = "abc"
=> "abc"
>> client.client_name = "ABC Company"
=> "ABC Company"
>> client.valid?
=> true
>> client.save
=> true