Question

I am trying to update another associated table before saving but i am getting into errors i am not familiar with…

so i have in my model

post.rb

  before_save :update_total_items

  def update_total_items
    b = Tags.find(:tag_id => self.tag_id)
    b.total_items = b.total_items+1
    b.save
  end

but i get an error

Unknown key tag_id

so how can i access the property i am adding before i save it in order to use it and update an existing associated on another table?

Answer 1

Usually the id of a model is called just that. Generally what you want is:

b = Tags.find(self.tag_id)

Be aware this might throw an ActiveRecord::RecordNotFound exception if no record could be found. A safer approach is:

if (b = Tags.where(:id => self.tag_id).first)
  b.increment!(:total_items)
end

Avoid loading and saving to increment a value. You may end up with an ugly race condition where you lose counts.

As a note, it’s highly irregular that your model is called Tags. It should be called Tag.