ruby on rails - How do I change an existing Comment model so it can belong to many different Models? -

ruby on rails - How do I change an existing Comment model so it can belong to many different Models? -

in rails app, comment belongs_to page (and stores page_id), while page has_many comments. want comment belong model well, picture. railscasts on polymorphic associations discusses how set commentable intermediary between comment , models belong_to.

however, have existing comment - page setup. how migrate database column , info on new commentable setup nil breaks?

try this:

rename column page_id commentable_id , create additional column called commentable_type , set default: 'page' previous info in table appropriate.

the migrations should be:

1) migration renaming page_id commentable_id

class renamecolumnpageidtocommentableidincomments < activerecord::migration def rename_column :comments, :page_id, :commentable_id end def downwards rename_column :comments, :commentable_id, :page_id end end

2) migration adding commentable_type

class addcolumncommentabletypetocomments< activerecord::migration def add_column :comments, :commentable_type, :string, default: 'page' end def downwards rename_column :comments, :commentable_type, end end

you need alter controller code comments views. hope helps :)

ruby-on-rails ruby-on-rails-4 polymorphic-associations rails-migrations