# Model Validation with Multiple Models and Good MVC Design

**URL:** <https://www.ruby-forum.com/t/model-validation-with-multiple-models-and-good-mvc-design/125253>\
**Category:** Rails\
**Created:** [January 7, 2008, 3:27pm UTC](https://www.ruby-forum.com/t/model-validation-with-multiple-models-and-good-mvc-design/125253 "2008-01-07T15:27:06Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![yinkyank](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/d9b06d/32.png) [@yinkyank](https://www.ruby-forum.com/u/yinkyank)\
**Post date:** [January 7, 2008, 3:27pm UTC](https://www.ruby-forum.com/t/model-validation-with-multiple-models-and-good-mvc-design/125253/1 "2008-01-07T15:27:06Z")

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1. Model Validation With Multiple Controllers Involved  
I have a Posts controller and model and a Comments controller and  
model. Posts has a show method and a corresponding view that shows a  
post and its associated comments, which are rendered with a partial  
from comments. Another partial from comments is used to allow the user  
to add their comment to the page.

Problem: If a user tries to add a new comment but it fails the comment  
model validation, how do I get back to the show page from posts and  
display the model validation error for the new comment?

views/posts/show.rhtml  
#spit out the details of the post  
…  
#render the existing comments and let a user make a new one

## Comments
\<%= render :partial =\> "comments/comment", :collection =\> @post.comments %\> \<%= render :partial =\> "comments/new"%\>

controllers/comments\_controller.rb  
#new method unnecessary because the “comments/new” partial never calls  
it?  
def new  
@comment = Comment.new  
end

def create  
@comment = Comment.new(params[:comment])  
if @comment.save  
redirect\_to :controller =\> “posts”, :action =\> “show”, :id =\>  
@comment.post  
else  
#we’re over in the comments controller - how do we get our data  
validation errors from the  
#comments model back over to the show page of posts?  
render :controller =\> “posts”, :action =\> “show”  
end

1. Good MVC Design  
OK so for my little blog app at first I had just one controller, blog,  
and just kept adding methods there like add\_post, add\_comment, etc. It  
seemed like maybe that was a bad idea so I decided to use three  
controllers instead of one: blog, posts, and comments. Blog would be  
light-weight and not have to care about the details of posts or  
comments. But then I ran into the problem described above.

What would be the most natural way to structure this kind of thing  
with MVC, one blog controller with double-barelled methods like  
add\_post, add\_comment etc. or a bunch of controllers like posts,  
comments, etc. that do all the heavy lifting?

Thanks,  
Yink