ActiveRecord + ActiveAdmin, save a empty string instead of null

Question

When I use the Active Admin form, the empty string values are saved as "" (empty) instead of NULL value.

Is there a parameter I should set in the initializer to save every empty values as NULL in MySQL?

form do |f|
    input :label
    input :description, as: :text
    input :country
    input :city
  end
  actions
end

This is my migration schema:

create_table "projects" do |t|
  t.string "label", limit: "40"
  t.string "country", limit: "2"
  t.string "city", limit: "200"
  t.string "description", limit: 600
end

And this is my Gemfile.

gem 'rails', '~> 5.1.0.rc1'
gem 'mysql2', '>= 0.3.18', '< 0.5'
gem 'puma', '~> 3.0'
gem 'sass-rails', '~> 5.0'
gem 'uglifier', '>= 1.3.0'
gem 'turbolinks', '~> 5'
gem 'jbuilder', '~> 2.5'
gem 'active_model_serializers', '~> 0.10.5', require: true
gem 'kaminari'
gem 'inherited_resources', '~> 1.7'
gem 'activeadmin', '~> 1.0.0.pre5'
gem 'sidekiq', '~> 4.2.10'
gem "paperclip", "~> 5.1.0"
gem 'aws-sdk', '~> 2.3.0'

The form saves empty values as "" instead of NULL in the MySQL table. — Cornelius
– Cornelius, Commented May 3, 2017 at 16:55

Md. Farhan Memon · Accepted Answer · 2017-05-03 17:26:53Z

1

That seems to be the default behaviour of forms. I came accross this gem nilify_blanks which will solve your issue. Hope it helps.

answered May 3, 2017 at 17:26

Md. Farhan Memon

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3 Comments

Cornelius Over a year ago

I saw the gem but the build flag has an error status. And I thought is was deprecated

Md. Farhan Memon Over a year ago

I see that too, but you can try and let me know if it breaks ur code, worth a try if you want it for all models keeping it dry. And I think you might have came accross this solution too if not see stackoverflow.com/a/40387633/6548745. It is good for limited attributes.

Md. Farhan Memon Over a year ago

so which one worked for you? gem or code from the SO link? @Cornelius

Piers C · Accepted Answer · 2017-05-05 00:52:27Z

1

This is a Rails, not an ActiveAdmin issue.

If you can, don't use null for empty strings. Using null may be theoretically correct, but in practice I have found working with MySQL simpler and less error prone if all varchar columns are set not null, e.g.:

t.string :label, limit: 40, null: false

The nilify_blanks gem is unmaintained since Rails 4. Instead, try the following in your model:

def label=(label)
  write_attribute :label, label.present? ? label : nil
end

edited May 5, 2017 at 0:52

answered May 4, 2017 at 23:53

Piers C

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1 Comment

ruurd Over a year ago

Yes well that's your opinion however from the PoV of truth maintenance, null is someting entirely different than an empty value or a default. In a lot of cases null signals that the value is not known while an empty value signals that the value is known but empty. I don't think it will be surprising that I disagree with you here.

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