Rails Active Record，如何在查询结果中添加其他字段参数？

Question

I actually have this model:

class Role < ActiveRecord::Base
  acts_as_authorization_role

  def self.all_join_wisp
    self.connection.select_all("SELECT roles.*, wisps.name AS wisp_name FROM roles LEFT JOIN wisps ON wisps.id = roles.authorizable_id")
  end
end

the method all_join_wisp does almost what I want, it adds the field wisp_name, except it return a hash and not an active record object.

Is there a way to retrieve an active record object instead?

The Role model does not have belongs_to and the wisp model does not have has_many :roles , I guess it was done for flexibility or something (I did not develop the application I'm working on).

Edit: Solution implemented

Solution implemented here: https://github.com/nemesisdesign/OpenWISP-Geographic-Monitoring/blob/287861d95fffde35d78b76ca1e529c21b0f3a54b/app/models/role.rb#L25 Thanks to @house9

Answer 1

you can use find_by_sql - you get back what looks like an activerecord object but isn't really, it will have attributes from your query but they will all be string data types instead of the real types, often this is ok

def self.all_join_wisp
  self.find_by_sql("SELECT roles.*, wisps.name AS wisp_name FROM roles LEFT JOIN wisps ON wisps.id = roles.authorizable_id")
end

then

list = Role.all_join_wisp
list.each do |x|
  puts x
  puts x.inspect
  puts x.id # the role id 
  puts x.id.is_a?(Integer) # false
  puts x.id.is_a?(String) # true
  puts x.name # the role name
  puts x.wisp_name # wisp name, NOTE: Role does not really have this attribute, find_by_sql adds it
end

Answer 2

model

class Role < ActiveRecord::Base

      def self.do

        joins("LEFT JOIN wisps w ON
                w.id = roles.id").select("roles.*,
                                          wisps.name AS wisp_name")    

      end

    end

controller

@roles = Role.do

@wisps = @roles.map {|i| i.wisp_name}

view

<%= @wisps %>