Custom ransacker for Active Admin

custom_ransacker.rb

# Custom search ransacker
# models/concerns/ransackers

module Ransackers
  module Candidate
    extend ActiveSupport::Concern

    included do
      ransacker :candidate_approved_at,
                formatter: proc { |date|
                             last_review = ReviewStatusChange.select('DISTINCT ON (candidate_id) candidate_id, review_status_id, created_at')
                                                             .order(:candidate_id, created_at: :desc).to_sql
                             joins("JOIN (#{last_review}) AS last_review ON last_review.candidate_id = \"Candidates\".id")
                               .where("last_review.created_at >= '#{date}'").where(last_review: { review_status_id: 2 })
                               .map(&:id)
                           } do |parent|
        parent.table[:id]
      end
    end   
  end
  
# ransacker implementation in active admin view

    filter :candidate_approved_at_in_all, label: 'Candidate approved', as: :select,
                                        collection: proc { days_ago_select_values([1, 3, 7, 14, 30]) }