Filtering (search) a model with multiple params in hash This function in my Profile model receive a hash from a search form and should filter the table depending on those values. I guess there is something like a pattern for such a standard behavior, right now I ended up with this (unfortunately I had to reproduce the code here, so it might not work for some reasons, but you get the idea).

Just a note: we're storing in the model some strings containing multiple data, each of these fields should be a one-to-many relationship (db normality violation). I give an example: country_preferences is a string filled up by an html select :multiple =&gt; true. In the string I then find values like: ["Australia", "China", "United Kingdom"].

  def search opts # This default doesn't work the way I would like = {:user_type =&gt; :family}

    #TODO: default opts value in method sign if possible
    opts[:user_type] ||= :family

    # initial criteria
    fields= "user_type= ?"
    values= [opts[:user_type]]

    # each field filters the list in one of these three ways
    staight_fields = [ :country, :first_name, :last_name, :nationality ]
    like_fields = [:country_preferences, :keyword, :languages ]
    bool_fields = [:driver, :housework, :children ]

    # cicle the options and build the query    
    opts.each do |k, v|
      if straight_fields.include? k
        fields += " AND #{k} = ?"
        values += v
      elsif like_fields.include? k
        fields += " AND #{k} like %?%"
        values += v
      elsif bool_fields.include? k
        fields += " AND #{k} = ?"
        values += v == 'true'
      else
        logger.warn "opts #{k} with value #{v} ignored from search"
      end
    end

    # execute the query and return the result
    self.registered.actives.where([fields] + values)   
  end


I think I can use more scope but how can I combine them together? In general, how can I make this code much better?

The boss, when introducing the project, said one-to-many relationships for that kind of fields would be a pain in the back. What do you think about this pragmatic solution?
Have you looked into using a pre existing gem for this? I found one called has_scope that seems like it might do exactly what you're trying to refactor. You would need to add a scope for each of your filters and then add some has_scope calls in your controller.

Here's a few examples. I'm not as familiar with Rails 3 scopes as I am with 2, so the code likely won't work as is.

Model:

class Profile &lt; ActiveRecord::Base
  scope :country, lambda {|country| where(:country =&gt; country) }
  scope :keyword, lambda {|keyword| where(["keyword LIKE :term", {:term =&gt; "%#{keyword}%"}]) }
  scope :driver, where{:driver =&gt; true)
end


Controller:

class ProfileController &lt; ApplicationController
  has_scope :country
  has_scope :keyword
  has_scope :driver, :type =&gt; :boolean
end