How to display the total number of items?

Question

Ruby on Rails

I'm using Rails 5.1.6 and the kaminari gem and api-pagination for pagination. And at the moment I have 10 records on one JSON page, but how can I add the total number of records on each json page? If I'm not mistaken, then you need to add ":collection => @posts" to the render, but this does not work for me.

class PostsController < ApplicationController

  def post
    posts = paginate Post.all, per_page: 10
    render json: JSON.pretty_generate(posts.as_json)
  end

  def index
    post
  end

end