Invalid nested resource added to collection before save in Rails 4 -

this routes.rb

resources :posts     resources :comments end 

and post/show.html.haml

.post   %h1= @post.title   %p= @post.content    - @post.comments.each |comment|      .comment         %h3= comment.name         %p= comment.text  = form_for([@post, @post.comments.build])  |f|   = f.label :name   = f.text_field :name   = f.label :text   = f.text_area :text   = f.submit 

the problem when try save invalid comment still gets added @post.comments , printed out. if refresh invalid comment disappears, still want avoid if possible - , wondering best practice is?

currently i'm working around issue doing check:

- unless comment.invalid? 

any appreciated! :-)

if wants know, solved problem in following way:

= form_for([@post, @comment = @comment || @post.comments.build)