find_one

# File activerecord/lib/active_record/relation/finder_methods.rb, line 296
    def find_one(id)
      id = id.id if ActiveRecord::Base === id

      record = where(primary_key.eq(id)).first

      unless record
        conditions = arel.where_sql
        conditions = " [#{conditions}]" if conditions
        raise RecordNotFound, "Couldn't find #{@klass.name} with ID=#{id}#{conditions}"
      end

      record
    end