How to show error messages in pop up or confirm screen ?

Adriano Lul wrote:

I would like to show messages when the validation fails (must be number,
cant be blank, etc) but not in the main page I would like to open a pop
up or better yet put it in a confirm screen where user would read and
thereafter click ok.

render :update do |page|
   if obj.save
     ...
   else
     page.alert obj.errors.full_messages.join("\n")
   end
end

even for validation models ?
THanks!!!