Ruby on Rails: How to have multiple controllers for one table AND multiple models

Question

I'm new to Ruby and to Rails. I have played a bit with Sinatra but I think that Rails is a more complete framework for my project. However, I am running into trouble with this.

I am working with an fairly substantial existing, and heavily used, mySQL database and I am trying to build an API for this that will report on certain features. The features that are needed are, for the most part, counts of records by certain groupings, then drilling down into details.

For example we have a table - tableA, that contains lots of information relating to documentation. One piece of information we want to report on from that is the number of items in a given language. The language code is stored against each item and based on a get request I would like to return JSON.

Request: /languages/:code/count/:tablename

There are two variables in that most specific URL - the code we are counting and the table we are counting from.

I understand that in routes.rb I can set up a mapping:

get '/languages/:code/count/:table', :controller=>'languages', :action=>'count'

I have a controller - languages_controller.rb with a count method in it. this then matches to a corresponding view file count.html.erb

In all the tutorials I have read and examples I have followed the main point seems that 'languages' would be a table in the database and would therefore be available under the 'magic' Rails approach.

My issue is that it is not a table, rather the results of the call should be a limited subset of the fields in tableA. Such as languagecode and count(id).

The description of the language needs to be looked up 'manually' as it is stored as an internal code that is not in a database anywhere (historic decision/madness).

The questions:

1. how do I have a model that is only a subset of fields, plus some that are manually populated - languagecode, isocode, description, count
2. Am I right in thinking that once I have the model defined as such as I could use ActiveRecord to get data from the database and then in the controller add the extra information in?
3. Can I change table in the model based on the parameter sent in the URL?

Essentially, I am at a loss at the moment on what to do with this. I have the routes defined, the view templates in place and the controller there and ready to go. The database component - getting some data from a pre-existing table seems mysterious to me.

Any help is greatly appreciated, it seems that the framework is currently getting in my way and I know that I can't be the only one trying this sort of thing so if you have any advice please share.

Answer 1

There's really no need for a model here, at all. This isn't what ORMs are for. What you should be doing is just running raw SQL against the database, and iterating over the results. Consider doing something like this: https://stackoverflow.com/a/14840547/229044