Rails equivalent of ApplicationController for models

Question

I understand that application_controller.rb is the place to put all the methods, etc that you would like made available in all your controllers since they all inherit from this class. Great.

But what is the equivalent for Models? In other words, I want a place where I can create a couple of super classes that my models will inherit from.

For example, I have a method that searches different tables for entries in all CAPS via REGEXP in Mysql. I'd like to be able to create the method only once and call it for different tables/models.

What is the Rails way of doing this?

I thought I could create a class that would inherit from ActiveRecord::Base (as all models do) , put the methods in there and then inherit all my models from that class. But thought there would surely be a better way to do it.

Thanks.

Edit

Per Semyon's answer I'm editing the post to show the routes I am using. It works now:

# models/dvd.rb
require 'ModelFunctions'
class Dvd < ActiveRecord::Base
    extend ModelFunctions
    ...
end

# lib/ModelFunctions.rb
module ModelFunctions
    def detect_uppercase(object)
        case object
        ...
        where("(#{field} COLLATE utf8_bin) REGEXP '^[\w[:upper:]]{5,}' ").not_locked.reorder("LENGTH(#{field}), #{table}.#{field} ASC")
    end
end

In config/application.rb

config.autoload_paths += %W(#{config.root}/lib)

Answer 1

Take a look at mixins, for example here:

http://ruby-doc.org/docs/ProgrammingRuby/html/tut_modules.html

In a Rails app you could create a module in the lib directory that defines your methods and then include it in your models.

EDIT: To be specific for your example, you're trying to define a class method. You can do this in a mixin like this:

module Common
  module ClassMethods
    def detect_uppercase(object)
      case object
      when 'dvd'
          field = 'title'
      ... 
      end    
      where("(#{field} COLLATE utf8_bin) REGEXP '^[\w[:upper:]]  {5,}').not_locked.reorder('LENGTH(title), title ASC')"
    end
  end

  def self.included(base)
    base.extend(ClassMethods)
  end
end

Now when you include Common in your model, that model's class will be extended to include the new class methods, and you should be able to call Dvd.detect_uppercase.

Answer 2

Put the reusable method in some module next to your Dvd class. You can move it in a separate file later.

# app/models/dvd.rb
module CaseInsensitiveSearch
  def case_insensitive_search(field, value)
    # searching field for value goes here
  end
end

class Dvd
end

After extending a class with the module you can use case_insensitive_search on the class. Including the module will make case_insensitive_search an instance method which is not what you want.

class Dvd
  extend CaseInsensitiveSearch
end

Dvd.case_insensitive_search("title", "foo")

And of course you can use it inside Dvd class.

class Dvd
  def self.search(query)
    case_insensitive_search("title", query)
  end
end

Dvd.search("foo")

Now when you made sure it works, you will probably want to move it in a separate file and use it across multiple classes. Place it in lib/case_insensitive_search.rb and make sure you have this line in config/application.rb:

config.autoload_paths += %W(#{config.root}/lib)

Now you can require it anywhere you want to use it:

require 'case_insensitive_search'

class Dvd
  extend CaseInsensitiveSearch
end

The last thing I'd like to suggest. Create multiple modules with meaningful names. So instead of CommonModel have CaseInsensitiveSearch and so on.