Filterable

filterable.rb

# Call scopes directly from your URL params:
#
#     @products = Product.filter(params.slice(:status, :location, :starts_with))
module Filterable
  extend ActiveSupport::Concern

  module ClassMethods
    
    # Call the class methods with names based on the keys in <tt>filtering_params</tt>
    # with their associated values. For example, "{ status: 'delayed' }" would call 
    # `filter_by_status('delayed')`. Most useful for calling named scopes from 
    # URL params. Make sure you don't pass stuff directly from the web without 
    # whitelisting only the params you care about first!
    def filter(filtering_params)
      results = self.where(nil) # create an anonymous scope
      filtering_params.each do |key, value|
        results = results.public_send("filter_by_#{key}", value) if value.present?
      end
      results
    end
  end
end

I had some issues using this with pundit gem policy scopes. I suggest renaming filter to filter_by. Has the benefit of consistent naming with scopes.