How to paginate Rabl's collections - ruby-on-rails

Question

I have this template:
# app/views/posts/index.rabl
collection #posts => :posts
attributes :id, :title, :subject
child(:user) { attributes :full_name }
node(:read) { |post| post.read_by?(#user) }
Witch returns:
{
"posts": [
{
"post": {
"id": 5,
"title": "...",
"subject": "...",
"user": {
"full_name": "..."
},
"read": true
}
}
]
}
And I would like to add to add some pagination params in order to rendering this:
{
"posts": [
{
"post": {
"id": 5,
"title": "...",
"subject": "...",
"user": {
"full_name": "..."
},
"read": true
}
}
],
"total": 42,
"total_pages": 12
}
Any ideas? Many thanks!

Answer 1

Sorry for my noob question, whitch was answered by the README. Here's an example of pagination:
object false
node(:total) {|m| #posts.total_count }
node(:total_pages) {|m| #posts.num_pages }
child(#posts) do
extends "api/v1/posts/show"
end
Note: I'm using Kaminari for pagination.

Answer 2

When searching for kaminari and rabl this is the first and pretty much only relevant result. As such, I would like to leave here a solution according to the HAL Specification that generates links like this.
So first, start with the view:
# api/v1/posts/index.rabl
object false
child(#posts) do
extends 'api/v1/posts/show'
end
node(:_links) do
paginate #posts
end
Then proceed to define the paginate method:
# app/helpers/api_helper
module ApiHelper
def paginate(collection)
current_page_num = collection.current_page
last_page_num = collection.total_pages
{
:first => first_page,
:previous => previous_page(current_page_num),
:self => current_page(current_page_num),
:next => next_page(current_page_num, last_page_num),
:last => last_page(last_page_num)
}
end
def first_page
{ :href => url_for(:page => 1) }
end
def previous_page(current_page_num)
return nil if current_page_num <= 1
{ :href => url_for(:page => current_page_num-1) }
end
def current_page(current_page_num)
{ :href => url_for(:page => current_page_num) }
end
def next_page(current_page_num, last_page_num)
return nil if current_page_num >= last_page_num
{ :href => url_for(:page => current_page_num+1) }
end
def last_page(last_page_num)
{ :href => url_for(:page => last_page_num) }
end
end
And finally, include the helper in the necessary controllers. The helper could be included in a Api::BaseController, from which all API controllers inherit:
helper :api
I could not have done this without Zag zag..'s solution, so.. Thank you so much!

Answer 3

note, for will_paginate 3.0.0 the following works:
node(:total) {|m| #posts.total_entries }
node(:total_pages) {|m| (#posts.total_entries.to_f / #posts.per_page).ceil }
node(:page_num){|m| #posts.current_page}

Answer 4

This might be what you are looking for ;)
object false
node :comments do
partial('posts/index', object: #posts)
end
node(:pagination) do
{
total:#posts.count,
total_pages: 20
}
end