Example model to persist Mongoid::Criteria as Searches

persisting_mongoid_criteria.rb

class Search
  include Mongoid::Document

  field :query, :type => Hash
  field :collection
  
  embedded_in :user

  def to_criteria
    Mongoid::Criteria.new( collection.titleize.constantize ).fuse( query )
  end
end


# Then you can store a criteria like this :
criteria = Product.where(:name => /Honda/, 'properties.color' => 'blue')
user.searches << Search.new(:query => criteria.scoped, :collection => criteria.klass.to_s)

# And retrieve it to use it later
search = user.searches.first.to_criteria
search.limit(10).to_a #=> array of 10 products matching your search