Question

I currently have the following controller method:

def update_all

    params[:users].each do |product, user|
       @product = Product.find(product)
       @product.update_attribute(:user_id, user)
    end
    redirect_to :back, :flash => { :notice => "Updated users" }
  end

This works as expected, however the problem is that the params are being passed via a select_tag, which has a default value — so if just one select tag is changed and the form is submitted, all the other records will be updated to the default value. How can I check if the attribute has change from its previous value, and only if it has changed to update it?

Answer 1

you can check for dirty attributes and presence

params[:users].each do |product, user_id|
  @product = Product.find(product)

  if user_id != '--' && user_id != @product.user_id
    @product.update_attribute :user_id, user
  end

  # or
  # if user_id != '--'
  #   @product.user_id = user_id
  #   @product.save if @product.user_id_changed?
  # end
end

or set the default values in your select tag (from Sending extra param value via select_tag)

<%= collection_select :user, :id, User.all, :id, :name, { selected: product.user_id }, { name: "users[#{product.id}]" } %>

so you don’t have to worry about default values.