Rails 7 validation to prevents delete AdminUser if its last-CodePudding

I've got Rails 7 app with AdminUser model. There can be multiple Admins in which anyone can remove any administrator. How do I set the validation so that it blocks the possibility of deleting AdminUser if this one is the last one in the db?

In a nutshell I want to have always one undelitable AdminUser.

CodePudding user response：

First of all, I would add an AdminUser#destroyable? to allow checking in the frontend if a destroy is possible and if a link should be rendered in the view.

# in app/models/admin_user.rb
def destroyable?
  AdminUser.count > 1
end

This can be used in the view like this:

<%= link_to(admin_user_path ...) if admin_user.destroyable? %>

Then you can raise an exception when someone tries to destroy the last admin user.

# in app/models/admin_user.rb
before_destoy :do_not_destroy_last_admin

private

def do_not_destroy_last_admin
  raise(
    ActiveRecord::RecordNotDestroyed, "Last admin cannot be deleted" 
  ) unless destroyable?
end

CodePudding user response：

Use a callback like before_destroy.

class AdminUser < ApplicationRecord
  before_destroy :check_last
  ...
  private 

  def check_last
    return unless AdminUser.size < 2
    raise ActiveRecord::RecordNotDestroyed, 'Can\'t delete last Admin'
  end
end