Question

Is there a better way to ensure that I don’t delete the last record of a relation? I feel like this should be done through a validation, but could not make that stop the destroy action.

FYI – @organization is present because nested routes

class LocationsController < ApplicationController
....
....
  def destroy
    @organization = Organization.find(params[:organization_id])
    @location = @organization.locations.find(params[:id])
    count = Location.find_all_by_organization_id(@location.organization_id).count
    if count > 1
      @location.destroy
      flash[:notice] = "Successfully destroyed location."
      redirect_to @organization
    else
      flash[:notice] = "Could not destroy the only location."
      redirect_to @organization
    end     
  end
end

Answer 1

You might also consider the before_destroy callback (though I don’t think your version is all that bad):

http://edgeguides.rubyonrails.org/active_record_validations_callbacks.html#destroying-an-object