Question

I am trying to connect to an existing Sybase db using Rails and populate a few selection lists. Here’s what I have done so far:
1. Installed and configured FreeTDS
2. Installed TinyTDS gem

if I execute command tsql -S serverName -U userName, I’m able to query the data. I have my config/database.yml configured as such:

development:  
  adapter: sybase  
  host: <sybase_host>  
  port: <port_no>  
  username: <user>  
  password: <password>  
  database: <db>

I then tried generating a model via rails generate model sybase_db --skip-migration and editing the created app/models/sybase_db.rb file as follows:

class SybaseDb < ActiveRecord::Base  
  set_table_name "my_sybase_table"  
end

When I try to run SybaseDb.new command in rails console, it doesn’t seem to work. I’m pretty new to Rails so what am I doing wrong?

Thanks!

Answer 1

Everything looks right up to the part where you generate a model called sybase_db. A model in Rails is typically linked to a specific table in a database, not the whole database. Rails uses naming conventions to simplify the linking of tables and columns to models and attributes.

For example, if you have a model User with attributes name and email that is linked to a table in your database called users and having columns name and email then all sorts of wonderful Rails magic just works. You could start the rails console and execute User.all to produce a collection of all users in the database. Or you might do something like

> u = User.find_by_email '[e-mail]'
=> #<User id: 123, email: "[e-mail]", name: "Joe"...>
> u.name
=> "Joe"

If you have an existing database, however, chances are you’re going to have to explain in more detail to Rails how to map the names in Sybase to those in your Rails system. You have one case of this in set_table_name — if your Sybase table was named t_user with a primary key of user_id but it had columns name and email then you could create a Rails model like

class User < ActiveRecord::Base
  set_table_name "t_user"
  set_primary_key "user_id"
end

Here’s a discussion of this topic on Quora with a couple good links that you might use to go further.

Depending on how extensive your existing system is, you may find that all of the magic of Rails goes away. Rails helps us avoid all of this mapping this to that, and follows strong naming conventions to give us all sorts of wonderful coolness. If your existing system has strong and predictable naming conventions, and isn’t terribly far off from Rails’ way, you might be able to use Rails successfully.