CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-4rails-activerecord
Victor Ronin
Victor Ronin

Reputation: 23268

Validate that original value was nil in Rails

I want to add a validation to the model to check that a field (string) could be set to something only it's original value is nil.

How can I do this?

Actually two subquestions are:

Upvotes: 1

Views: 305

Answers (1)

evanbikes
evanbikes

Reputation: 4171

This seems like a custom job. Say you have a field named field.

validate :no_modifications_on_field

def no_modifications_on_field
  if field_changed? && !field_was.nil?
    errors.add(:field, 'Once you set a field, you can never change it!')
  end 
end

field_changed? and field_was are ActiveModel::Dirty helpers that get generated for every field. You can also access all changed attributes through changed_attributes.

Upvotes: 3

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