mysql - Rails: Force empty string to NULL in the database

Question

Is there an easy way (i.e. a configuration) to force ActiveRecord to save empty strings as NULL in the DB (if the column allows)?

The reason for this is that if you have a NULLable string column in the DB without a default value, new records that do not set this value will contain NULL, whereas new records that set this value to the empty string will not be NULL, leading to inconsistencies in the database that I'd like to avoid.

Right now I'm doing stuff like this in my models:

before_save :set_nil

def set_nil
  [:foo, :bar].each do |att|
    self[att] = nil if self[att].blank?
  end
end

which works but isn't very efficient or DRY. I could factor this out into a method and mix it into ActiveRecord, but before I go down that route, I'd like to know if there's a way to do this already.

Answer 1

Yes, the only option at the moment is to use a callback.

before_save :normalize_blank_values

def normalize_blank_values
  attributes.each do |column, value|
    self[column].present? || self[column] = nil
  end
end

You can convert the code into a mixin to easily include it in several models.

module NormalizeBlankValues
  extend ActiveSupport::Concern

  included do
    before_save :normalize_blank_values
  end

  def normalize_blank_values
    attributes.each do |column, value|
      self[column].present? || self[column] = nil
    end
  end

end

class User
  include NormalizeBlankValues
end

Or you can define it in ActiveRecord::Base to have it in all your models.

Finally, you can also include it in ActiveRecord::Base but enable it when required.

module NormalizeBlankValues
  extend ActiveSupport::Concern

  def normalize_blank_values
    attributes.each do |column, value|
      self[column].present? || self[column] = nil
    end
  end

  module ClassMethods
    def normalize_blank_values
      before_save :normalize_blank_values
    end
  end

end

ActiveRecord::Base.send(:include, NormalizeBlankValues)

class User
end

class Post
  normalize_blank_values

  # ...
end