Rails - Render array attribute as string on failed validation

Question

I have a form field where a user inputs a string of tags "foo, bar, foobar". This is sent to the controller as item_params[:tag_list]. In the controller my create action includes @item = Item.create(tag_list: item_params[:tag_list]). This causes the tag_list attribute to be populated as an array of strings ["foo", "bar", "foobar"].

When validation fails I need the input field of the form to be populated with "foo, bar, foobar" and not the array of strings. Is there a way to manipulate this before it goes back to populate the field of the form that failed validation?

what is the validation?

Harry Bomrah
– Harry Bomrah

2016-01-30 06:01:07 +00:00
Commented Jan 30, 2016 at 6:01 — Harry Bomrah
– Harry Bomrah, Commented Jan 30, 2016 at 6:01

Long Nguyen · Accepted Answer · 2016-01-30 05:49:28Z

0

Are you using acts-as-taggable-on gem? Hope this line can resolve you problem

f.text_field :tag_list, value: f.object.tag_list.join(', ')

Or you have to override tag_list method in Item model

alias_method :array_tag_list, :tag_list
def tag_list
  array_tag_list.join(', ')
end

edited Jan 30, 2016 at 5:49

answered Jan 30, 2016 at 3:28

Long Nguyen

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2 Comments

user4584963 Over a year ago

I wasn't able to get your suggestion to work. It might be because I am using bootstrap tag inputs and it is causing a problem. I was able to solve my problem by changing the tag_list attribute to a string if the validation fails. I did this in the controller @item.tag_list.remove(item_params[:tag_list], parse: true) then @item.tag_list.add(item_params[:tag_list])

Long Nguyen Over a year ago

I think you have to override tag_list method in Item model. alias_method :array_tag_list, :tag_list def tag_list array_tag_list.join(', ') end

Community · Accepted Answer · 2017-05-23 11:44:58Z

Highly surprised that the param is being treated as an array.

Sorry, misread your question (presumed you wanted validation message). Will leave for posterity:

Whenever you use a validation, you get access to three interpolations: value, attribute & model:

#app/models/item.rb
class Item < ActiveRecord::Base
   validates :tag_list, x: { message: "%{value} is not valid" }
end

According to the docs, you can pass a Proc for direct manipulation:

#app/models/item.rb
class Item < ActiveRecord::Base
   validates :tag_list, x: { message: ->(key, data) do
       "#{data[:value].join} is not valid"
    end 
   }
end

--

In order to populate the field, you'll want to use the value attribute of the attribute, populating with data from the form object:

= text_field :tag_list, value: f.object.tag_list.join

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