You're going to have to collapse those values into something that will fit in a URL, then decode them later. For instance:
# Put this in your helper method module PostsHelper
def post_ids
@posts.collect(&:id).join(',')
end
Your adjusted link would be:
link_to "newpage", {:controller => 'posts', :action => 'newmethod', :param => post_ids }
When you fetch the next page you'll need to decode these by retrieving them again:
@posts = Posts.find(params[:param].split(/,/))
There's no way to pass an instance variable between requests because they are explicitly cleared out.
As a note, try and use the generated route methods instead of the hash-style declaration. You would probably have a route already listed in rake routes:
# Instead of { :controller => 'posts', :action => 'new', :param => post_ids }
new_post_path(:param => post_ids)
These generated methods are much more readable in practice and have the advantage of being configurable later if you want to re-interpret what they mean by adjusting your routing table.
Another note is that if the list of IDs gets very large, you may not be able to encode them into a URL as the limit is about 1500 bytes. You may instead have to serialize the conditions used to generate the list in the first place and then re-run those again later. So long as you're dealing with tens of items and not hundreds you should be okay, though.
