Rails if语句形式为simple_form和HAML

Question

I have the following code in form that automatically puts the position of the object into input, using the if statement to eliminate this from happening when user edits.

- if @collection_page.new_record?
  = f.input :position, :label => "Display order:", input_html: { value: Spree::CollectionPage.last.position + 1 }
- else
  = f.input :position, :label => "Display order:"

I'm having trouble when there are no records and creating the first one, I get the usual nil class error.

undefined method `position' for nil:NilClass

Which makes sense because I don't have any records yet.

So just need to put a little more logic in there.

I tried:

- if @collection_page.new_record? || Spree::CollectionPage.last.position.present? # and @collection_page.last.position.present?

Without success

Looking for a clean way to achieve this, thank you in advance for your help!

Answer 1

You used an or statement. || is or, while && is and. Also, you're checking if last.position.present? which will not work if last is not present.

Try if @collection_page.new_record? && Spree::CollectionPage.last.present? if @collection_page.new_record? && Spree::CollectionPage.last.present?