# Wrap error\_messages\_for() call when no instance var present **URL:** \ **Category:** Rails\ **Created:** [March 20, 2006, 11:27pm UTC](https://www.ruby-forum.com/t/wrap-error-messages-for-call-when-no-instance-var-present/84405 "2006-03-20T23:27:30Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![weyus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7ab992/32.png) [@weyus](https://www.ruby-forum.com/u/weyus)\ **Post date:** [March 20, 2006, 11:27pm UTC](https://www.ruby-forum.com/t/wrap-error-messages-for-call-when-no-instance-var-present/84405/1 "2006-03-20T23:27:30Z")
I am trying to put some smarts around a call to \<%= error\_messages\_for %\> so that when I first come into this page i.e. when my instance variable @target\_list has not been defined yet, the page doesn’t break. I’m doing this: \<% if @target\_list? %\> \<%= error\_messages\_for ‘target\_list’ %\> \<% end %\> I get a syntax error on line 1. What is wrong with if @target\_list? to test for the existence of the @target\_list variable? Thanks, Wes ---
**Author:** ![weyus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7ab992/32.png) [@weyus](https://www.ruby-forum.com/u/weyus)\ **Post date:** [March 20, 2006, 11:35pm UTC](https://www.ruby-forum.com/t/wrap-error-messages-for-call-when-no-instance-var-present/84405/2 "2006-03-20T23:35:04Z")
\<%= error\_messages\_for ‘target\_list’ unless @target\_list.nil? %\> – Wes On 3/20/06, Wes G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > \<% if @target\_list? %\> > Wes > > – > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). > > * * * > > Rails mailing list > removed\_email\_address@domain.invalid > [http://lists.rubyonrails.org/mailman/listinfo/rails](http://lists.rubyonrails.org/mailman/listinfo/rails) – ``` -- Wes ``` ---
**Author:** ![weyus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7ab992/32.png) [@weyus](https://www.ruby-forum.com/u/weyus)\ **Post date:** [March 21, 2006, 12:01am UTC](https://www.ruby-forum.com/t/wrap-error-messages-for-call-when-no-instance-var-present/84405/3 "2006-03-21T00:01:01Z")
Wes, Thanks! That gets around the original problem of the initial display but the error\_messages\_for method doesn’t appear to be able to handle the instance variable target\_list. The controller method [let’s call it x] that my page posts to has the following code def x @target\_list = TargetList.create() @target\_list.name = name @target\_list.save! … and my model for TargetList has :validates\_presence\_of :name So, if I call x based on the post from my form which includes \<%= error\_messages\_for ‘target\_list’ unless @target\_list.nil? %\> I get an ugly “Record Invalid” message when I call save! instead of the error\_messages\_for output. Does this not work because the initial definition of the @target\_list instance variable in the controller is within method x? I wish I could get helper methods to actually work in non-trivial cases. I'm not trying to use a scaffold to do my model managmeent and it seems to me that \_because\_ I'm not using a scaffold, I can't take advantage of any of these helper things. Thanks for any insight, Wes Wes Garrison wrote: > \<%= error\_messages\_for ‘target\_list’ unless @target\_list.nil? %\> > > – Wes > > On 3/20/06, Wes G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > \<% if @target\_list? %\> > > Wes > > > > – > > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). > > > > * * * > > > > Rails mailing list > > removed\_email\_address@domain.invalid > > [http://lists.rubyonrails.org/mailman/listinfo/rails](http://lists.rubyonrails.org/mailman/listinfo/rails) > > – > > ``` > -- Wes > > ``` ---
**Author:** ![weyus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7ab992/32.png) [@weyus](https://www.ruby-forum.com/u/weyus)\ **Post date:** [March 21, 2006, 12:22am UTC](https://www.ruby-forum.com/t/wrap-error-messages-for-call-when-no-instance-var-present/84405/4 "2006-03-21T00:22:39Z")
I don’t really use that helper. With that warning in place… First, try: @target\_list.save … without the ! that forces it to save in place. Normally, I do this: if @target\_list.save flash[‘notice’] = “Yay!” redirect\_to :action =\> ‘list’ else flash[‘error’] = “Nay?!” render :action =\> ‘new’ end Someone else feel free to chime in with “error\_messages\_for” help… – Wes PS: Stop taking all the “wesg” login names everywhere. On 3/20/06, Wes G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > following code > > instance variable in the controller is within method x? > Wes Garrison wrote: > > > > * * * > > – > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). > > * * * > > Rails mailing list > removed\_email\_address@domain.invalid > [http://lists.rubyonrails.org/mailman/listinfo/rails](http://lists.rubyonrails.org/mailman/listinfo/rails) – ``` -- Wes ``` ---
**Author:** ![weyus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7ab992/32.png) [@weyus](https://www.ruby-forum.com/u/weyus)\ **Post date:** [March 21, 2006, 12:26am UTC](https://www.ruby-forum.com/t/wrap-error-messages-for-call-when-no-instance-var-present/84405/5 "2006-03-21T00:26:32Z")
My logins are all wgamble so I don’t wanna hear any crap :)… Thanks for the advice. I just need to understand how all this magic works - I can’t just accept it. That will be my ultimate problem in adopting Rails. I’m ok with magic if it’s consistent and there are clear rules around it. But the magic here _appears_ to be highly context-specific and it’s starting to get on my nerves :). On the other hand, I really love ActiveRecord so far. It’s the view stuff (that I am terrible at to begin with) that is really getting my goat… WG Wes Garrison wrote: > I don’t really use that helper. With that warning in place… > > First, try: > @target\_list.save > … without the ! that forces it to save in place. > > Normally, I do this: > if @target\_list.save > flash[‘notice’] = “Yay!” > redirect\_to :action =\> ‘list’ > else > flash[‘error’] = “Nay?!” > render :action =\> ‘new’ > end > > Someone else feel free to chime in with “error\_messages\_for” help… > > – Wes > > PS: Stop taking all the “wesg” login names everywhere. > > On 3/20/06, Wes G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > following code > > > > instance variable in the controller is within method x? > > Wes Garrison wrote: > > > > > > * * * > > > > – > > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). > > > > * * * > > > > Rails mailing list > > removed\_email\_address@domain.invalid > > [http://lists.rubyonrails.org/mailman/listinfo/rails](http://lists.rubyonrails.org/mailman/listinfo/rails) > > – > > ``` > -- Wes > > ``` ---
**Author:** ![weyus](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7ab992/32.png) [@weyus](https://www.ruby-forum.com/u/weyus)\ **Post date:** [March 21, 2006, 4:50pm UTC](https://www.ruby-forum.com/t/wrap-error-messages-for-call-when-no-instance-var-present/84405/6 "2006-03-21T16:50:54Z")
If you haven’t yet, take a look at the api [http://api.rubyonrails.com](http://api.rubyonrails.com) for ActiveRecord::Validations It’s got an explanation of the Errors object there and how it gets loaded on validation. When I have a behind-the-scenes question, I use the API and read the source for the functions I’m interested in. That really helps me to know what’s actually happening, plus I get to see cool Ruby tricks that I didn’t know otherwise. – The Real WG