forgeplus/app/models/pm_link.rb

# == Schema Information
#
# Table name: pm_links
#
#  id               :integer          not null, primary key
#  be_linkable_type :string(255)      not null
#  be_linkable_id   :integer          not null
#  linkable_type    :string(255)      not null
#  linkable_id      :integer          not null
#  created_at       :datetime         not null
#  updated_at       :datetime         not null
#
# Indexes
#
#  index_pm_links_on_linkable_id    (linkable_id)
#  index_pm_links_on_linkable_type  (linkable_type)
#

class PmLink < ApplicationRecord
  belongs_to :linkable, polymorphic: true
  belongs_to :be_linkable, polymorphic: true
  # belongs_to :linkable_issue, -> {where(pm_links: {linkable_type: 'Issue'})}, foreign_key: 'linkable_id', class_name: 'Issue'
  # belongs_to :be_linkable_issue, -> {where(pm_links: {be_linkable_type: 'Issue'})}, foreign_key: 'be_linkable_id', class_name: 'Issue'

  def be_linkable
    be_linkable_type.constantize.find be_linkable_id
  end
end