can display relation between author

app/controllers/desktop/co_authors_controller.rb

@@ -1,6 +1,7 @@
 class Desktop::CoAuthorsController < ApplicationController
   def index
     @co_authors = CoAuthor.where(name_id: current_user.id)
+    @co_author_relations = CoAuthorRelation.all
 
     respond_to do |format|
       format.html { render :layout => false}
@@ -27,6 +28,7 @@ class Desktop::CoAuthorsController < ApplicationController
 
   def edit
     @co_author = CoAuthor.find(params[:id])
+    @co_author_relations = CoAuthorRelation.all
     respond_to do |format|
       format.html { render :layout => false}
     end

app/models/user/co_author.rb

@@ -6,9 +6,8 @@ class CoAuthor
   field :name_id, type: BSON::ObjectId
   field :co_author, localize: true
   field :email
-  field :type
 
-  has_and_belongs_to_many :co_author_relations
+  belongs_to :co_author_relations
 
   VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/
   validates :email, format: { with: VALID_EMAIL_REGEX },

app/views/desktop/co_authors/_form.html.erb

@@ -17,7 +17,7 @@
 
 
   <%= f.label :type%><br />
-  <select name="co_author[type]" id="" class="s_grid s_grid_4">
+  <select name="co_author[co_author_relations_id]" id="" class="s_grid s_grid_4">
     <%= options_for_select(
       @co_author_relations.map do |relation|
         [relation.relation, relation.id]

app/views/desktop/co_authors/index.html.erb

@@ -17,7 +17,8 @@
   <tr>
     <td><%= co_author.co_author %></td>
     <td><%= co_author.email %></td>
-    <td><%= co_author.type%></td>
+    <td><%= @co_author_relations.find(co_author.co_author_relations_id).relation \
+                unless co_author.co_author_relations_id.nil?%></td>
     <td><%= link_to 'Edit', edit_desktop_co_author_path(co_author), :class => "bt-edit" %></td>
     <td><%= link_to 'Destroy', desktop_co_author_path(co_author), method: :delete, confirm: 'Are you sure?', :class=>"bt-delete"  %></td>
   </tr>