How to check if attribute is changing in update action in Rails?

Question

I'm trying to check - if some (language) attribute is changed and if it is equal to some value I need to change it into other proper value.

Here is my code:

EDIT:

    def update
@website = Website.find(params[:id])
@website.language = params[:website][:language]
if @website.language_changed?
  if params[:website][:language] == "Automatic (by user's browser language)"
    @website.language = full_language(request.env['HTTP_ACCEPT_LANGUAGE'].scan(/^[a-z]{2}/).first)
  end
end
respond_to do |format|
 if @website.save
   format.html { redirect_to @website, 
  notice: 'Note: code has been updated. Please replace the code you have on your website with the code below. Only then changes will take effect.' }
   end
  end
end

My form:

  <%= f.label "Website category"%>
  <%= f.select :category, options_for_select([
      "--- please select ---",
      "Banking",
      "Computers]) %>
  <%= f.label "Language preferences"%>
  <%= f.select :language, options_for_select([
       "--- please select ---",  
       "Automatic (by user's browser language)",
        "Arabic",
        "Chinese"]) %>

And when I'm changing category - it changint language to default. How can I prevent this ?

Gives me error:

   undefined method `updated?' for "--- please select ---":String

What I'm doing wrong ?

try `@website.changes` - return the hash, on the left is what was in object, on the right - what will be. — Denis Tataurov, Oct 04 '12 at 14:17

score 5 · Accepted Answer · answered Oct 04 '12 at 14:49

5

I just tried this via the console, and it looks like ActiveRecord isn't tracking the change when you do a mass attribute update like @website.attributes = params[:website]. It may be simpler to just do something like if @website.language != params[:website][:language] (and move your update somewhere later, of course.). A little uglier, I realize, but it would work. Of course, you can always look at enhancing your model to track changes from mass updates.

Regarding the fields changing - it sounds like your select list is not initializing to the correct values. If the value of @website.category is "foo", then when this page loads the select list should have "foo" selected. That doesn't seem to be happening, so when you submit the form and do your mass attribute update, its updating the category attribute to whatever list item was selected by default.

answered Oct 04 '12 at 14:49

Scott S

2,696
16
20

Thanks, @Scott how can I initialize selectBox with correct value ? – Denys Medynskyi Oct 04 '12 at 14:50
How can I change category and language separately ? – Denys Medynskyi Oct 04 '12 at 14:51
When you are doing `form_for` you should be able to be able to specify `form_for @website`, where @website is an object that was initialized in the action for this view. If you're doing those things I would think the helpers would initialize the select list for you. If not, check the docs for the rails select helper - you should be able to pass in the currently selected value to force it to initialize to that value. – Scott S Oct 04 '12 at 15:05
You mean, make first option = @website.category ? – Denys Medynskyi Oct 04 '12 at 15:08
Actually, I just noticed that where you're calling your select helper you have `"Computers])` - there is no ending quote on the "Computers" value. Is that just a typo in your post? – Scott S Oct 04 '12 at 15:27

Amar · Answer 2 · 2012-10-04T14:58:43.270

0

@website.language_changed? is method,you can watch http://railscasts.com/episodes/109-tracking-attribute-changes

def update
  @website = Website.find(params[:id])

  if params[:website][:language] == "Automatic (by user's browser language)" &&  @website.language != params[:website][:language]
    params[:website][:language] = full_language(request.env['HTTP_ACCEPT_LANGUAGE'].scan(/^[a-z]{2}/).first)
  end
  if @website.update_attributes(params[:website])
  end

end

edited Oct 04 '12 at 14:58

answered Oct 04 '12 at 14:17

Amar

6,874
4
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23

ok, thanks. But when I'm changing value in one select list the other field is changin. – Denys Medynskyi Oct 04 '12 at 14:19
other field is changing? i don't get it might be you want only language field to be set `@website.language=params[:website][:language]` – Amar Oct 04 '12 at 14:26
I mean when I'm changing category - language is changing to default, when I'm changin language - category is changin too. – Denys Medynskyi Oct 04 '12 at 14:27
I want to make it stay the same until user is changing it. – Denys Medynskyi Oct 04 '12 at 14:29
so you don't want to change category while changing language if this is your case then `@website.attributes = params[:website]` use `@website.language=params[:website][:language]` – Amar Oct 04 '12 at 14:30
When I;m trying `if @website.language_updated?` started to give me `undefined method `language_updated?'` – Denys Medynskyi Oct 04 '12 at 14:33
it's not updated kindly refer answer it's `@website.language_changed?` – Amar Oct 04 '12 at 14:35
I will post code - and you will tell why it is continue to change, ok ? – Denys Medynskyi Oct 04 '12 at 14:36
as per your code and comment i think you have change your question ,your initial question for updated? undefined method – Amar Oct 04 '12 at 15:04
Missunderstanding) When I'm changin ONE attribute - second is changing to ( into default selectbox value ) how can I prevent this ? – Denys Medynskyi Oct 04 '12 at 15:06

How to check if attribute is changing in update action in Rails?

2 Answers2