Rails collection_select: save null instead of empty string when 'blank' option selected

Question

I have the following code for a select box in a form:

<div class="field">
  <%= f.label :user_id %>
  <%= f.collection_select :user_id, User.all, :id, :name, include_blank: true %>
</div>

And it displays the following select options:

I noticed that when the blank option is selected, what actually gets saved in the database is an empty string: ''

I do not want to save an empty string when the blank option is selected. Instead: I want to save null.

I attempted overriding the setter in the rails model but it didn't work:

def text_value=(value)
  write_attribute(:name, nil) and return if value.empty?
  super
end

How might I do this at the application level? I am aware that I could have a Default Value specified at the Database level, but it seems that this might be better suited at the application level.

Isn't that just a wrong representation that you are looking at? I mean, an integer field will never be an empty string. It can be either a number or null, right? — kriskova
– kriskova, Commented Nov 2, 2016 at 18:50
In this circumstance: no. If the blank option is selected then that would mean that the user has not selected an answer, thus null. Pretend that there is another select option that specifies 'does not apply' or 'no' and which actually saves a blank string value. Saving it as null in the database is just a way for me to say 'oh ok, they did not answer this question at all. — Neil
– Neil, Commented Nov 2, 2016 at 18:53

Neil · Accepted Answer · 2016-11-02 19:14:00Z

2

This works:

def text_value=(value)
  if value.empty?
    write_attribute(:name, nil)
  else
    super
  end
end

edited Nov 2, 2016 at 19:14

answered Nov 2, 2016 at 18:52

Neil

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Teoulas · Accepted Answer · 2016-11-02 19:27:28Z

2

If you want to do this for multiple attributes and/or models, there's a gem for that: https://github.com/rubiety/nilify_blanks

answered Nov 2, 2016 at 19:27

Teoulas

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