# Comments on blogs

**URL:** <https://www.ruby-forum.com/t/comments-on-blogs/73594>\
**Category:** Rails\
**Created:** [October 25, 2006, 4:03pm UTC](https://www.ruby-forum.com/t/comments-on-blogs/73594 "2006-10-25T16:03:35Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 25, 2006, 4:03pm UTC](https://www.ruby-forum.com/t/comments-on-blogs/73594/1 "2006-10-25T16:03:35Z")

</div>

So I’m building a blog application using Ruby on Rails, and when it  
comes to implementing comments I follow the example laid down in the  
blog example screencast. I’ve run into the same problem as several  
others; that I can’t work out how I’m supposed to set parameters in my  
comment creation method that aren’t given to it by the form view. So my  
comment controller has a method like this:

def create  
@post = Post.find(params[:id])  
@comment = @post.comments.create(params[:comment])  
@comment.datetime = Time.now # Doesn’t work!  
@comment.user\_id = @user.id # Doesn’t work!  
if @comment.save  
flash[:note] = ‘Comment was successfully created.’  
redirect\_to :action =\> ‘list’  
else  
render :action =\> ‘new’  
end  
end

The post ID is established correctly, my relationships are set up as  
they should be in my models, and the :comment params are being passed  
successfully, but the two lines after I create my @comment instance  
variable don’t seem to have any effect. I’m getting database errors  
saying there are NULL values where there shouldn’t be.

The only solutions I’ve found are to pass the values I want as hidden  
fields in my form (a security risk), or add them using :before\_create  
hooks. Am I missing something or can what I want not be done through  
the controller?

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 25, 2006, 4:29pm UTC](https://www.ruby-forum.com/t/comments-on-blogs/73594/2 "2006-10-25T16:29:40Z")

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hello,  
i don´t know what went wrong with the @comment.datetime line, would have  
to see your model/db for that.  
but the @comment.user\_id is pretty obvious.  
if you store the user id in a session for example, you would have to do  
something like this:

def create  
  
@user = User.find(:session[“user\_id”])  
@comment.user\_id = @user.id  
  
end

cheers,  
alexander

removed\_email\_address@domain.invalid wrote:

> ```
> @comment.datetime = Time.now # Doesn't work!
> 
> ```
> 
> they should be in my models, and the :comment params are being passed
> 
> >

–  
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---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 25, 2006, 4:51pm UTC](https://www.ruby-forum.com/t/comments-on-blogs/73594/3 "2006-10-25T16:51:45Z")

</div>

On 10/25/06, removed\_email\_address@domain.invalid [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> ```
> @comment = @post.comments.create(params[:comment])
> 
> ```
> 
> The post ID is established correctly, my relationships are set up as  
> they should be in my models, and the :comment params are being passed  
> successfully, but the two lines after I create my @comment instance  
> variable don’t seem to have any effect. I’m getting database errors  
> saying there are NULL values where there shouldn’t be.
> 
> The only solutions I’ve found are to pass the values I want as hidden  
> fields in my form (a security risk), or add them using :before\_create  
> hooks. Am I missing something or can what I want not be done through  
> the controller?

I assume @post.comments.create() tries to save the the comment right  
away, which fails because it isn’t fully initialized.

AR tends to write updates as you manipulate associations, so you can’t  
really build the object graph in memory and then save/update it all  
with a single call to save, as I (too?) assumed when I got started  
with rails. 😕

Either way, read your stack trace carefully, it tells you everything  
you need to know about where things blow up.

If my guess is correct, try to create a free-standing comment first,  
using Comment.new, then add it to the post once you’ve set all  
required fields. (@post.comments \<\< my\_comment)

You could also try @post.comments.build() to create an associated  
instance that isn’t saved right away, but i think the former approach  
is cleaner.

More info under ActiveRecord::Associations::ClassMethods in the API  
docs.

HTH,  
Isak

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<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 29, 2006, 3:28pm UTC](https://www.ruby-forum.com/t/comments-on-blogs/73594/4 "2006-10-29T15:28:52Z")

</div>

Hey Isak, you’re right that create() tries to save the object right  
away, however, there’s build, which doesnt save the object,  
so you get a comment object back with the post association already in  
filled, and you can then add further stuff and save it afterwards:

def create  
@post = Post.find(params[:id])  
@comment = @post.comments.build(params[:comment])  
@comment.datetime = Time.now # Doesn’t work!  
@comment.user\_id = @user.id # Doesn’t work!  
if @comment.save  
flash[:note] = ‘Comment was successfully created.’  
redirect\_to :action =\> ‘list’  
else  
render :action =\> ‘new’  
end  
end

So changing create to build should do the trick, assuming @user already  
exists by initializing it in the applications before\_filter or some  
other way …  
As a sidenote, i would prefer to allow the datetime property to be nil,  
and have the Database set it with a default value if empty…

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 29, 2006, 3:28pm UTC](https://www.ruby-forum.com/t/comments-on-blogs/73594/5 "2006-10-29T15:28:53Z")

</div>

Also a good idea, I’ve edited my database schema so my timestamps  
default to now().

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 25, 2006, 5:13pm UTC](https://www.ruby-forum.com/t/comments-on-blogs/73594/6 "2006-10-25T17:13:51Z")

</div>

Isak H. wrote:

> If my guess is correct, try to create a free-standing comment first, using Comment.new, then add it to the post once you've set all required fields. (@post.comments \<\< my\_comment)

Ah, that approach helped:

@post = Post.find(params[:id])  
@user = User.find(session[:user\_id])  
@comment = Comment.new(params[:comment])  
@comment.datetime = Time.now  
@comment.user\_id = @user.id  
@comment.post\_id = @post.id

Works!

I hadn’t realised the create method was trying to save the instance,  
that’s why my database was throwing up errors, because the INSERT was  
getting called prematurely.