Question

I need to validate a value’s presence, but only AFTER the value is populated. When a User is created, it is not required to set a shortcut_url. However, once the user decides to pick a shorcut_url, they cannot remove it, it must be unique, it must exist.

If I use validates_presence_of, since the shortcut_url is not defined, the User isn’t created. If I use :allowblank => true, Users can then have “” as a shortcut_url, which doesn’t follow the logic of the site.

Any help would be greatly appreciated.

Answer 1

Here we are always making sure the shortcut_url is unique, but we only make sure it is present if the attribute shortcut_selected is set (or if it was set and now was changed)

class Account 
  validates_uniqueness_of :shortcut_url
  with_options :if => lambda { |o| !o.new_record? or o.shortcut_changed? } do |on_required|
    on_required.validates_presence_of :shortcut_url
  end

end

You’ll need to test to make sure this works well with new records.