will paginate, nested routes, ruby, rails

Question

I'm trying to get will paginate to link to my nested route instead of the regular posts variable. I know I'm supposed to pass some params to paginate but I don't know how to pass them.

Basically there is an array stored in @posts and the other param paginate has access to is category_id.

The nested route is /category/1/posts but hitting next and previous on will paginate returns a url like this posts?page=1&category_id=7.

 <%= will_paginate @most_recent_posts "What do I do here?" %>

---

This is the result of Yannis's answer:

In your controller you can do:

@posts = @category.posts.paginate

And in your view:

<%= will_paginate(@post) %>

Doing this comes up with the following URL

posts?page=2&post_category_id=athlete_management

---

routes.rb #there are more routes but these are the relevant ones

map.resources :posts
map.resources :post_categories, :has_many => :posts

Answer 1

In your controller you can do:

@posts = @category.posts.paginate

And in your view:

<%= will_paginate(@post) %>

Answer 2

Okay, so it's not clear from the question exactly, but I'm assuming that you are trying to go from a root-level URL like /posts into pages for specific categories like /category/1/posts.

The reason I assume this is because I have nested routes (in a namespace even) where will_paginate works fine without any special params. If that is not the case then there is probably something else funky going on with your routes and more information will be needed to debug.

However I can at least explain how will_paginate works. When it's generating the page URLs it calls url_for with existing params plus the specific page needed. Therefore, if you already have a bunch of params set, it should preserve them, including ones that are part of the path itself. Fortunately it also allows you to pass additional params to merge in with the (surprise!) :params parameter to will_paginate.

Now assuming you have the nested routes set up properly, /category/1/posts can be generated by:

url_for(:controller => 'posts', 
        :category_id => '1')

But if you are on the page /posts then the params will only be:

{:controller => 'posts'}

So you need to pass the category_id to will_paginate like so:

<%= will_paginate @posts, :params => {:category_id => @posts.first.category_id} %>

If this doesn't work, then I suspect something wrong with your routes. Try putting a debug statement in the template and calling url_for with different permutations of the params. Remember that the route definition order matters and could be creating conflicts.