Question

I am trying to retrieve from my database all posts and list them in DESC order with respect to their creation date. So far I have managed to test for all posts that belong to one category but I want to display all posts no matter what category they belong to. I know I have to loop trough each category, and get the posts from each but I dont know how to. Here is my code:

EDIT:

  def index
    @institution = Institution.find(current_user.institution.id)
    @categories = Category.all
    @categories.each do |category|
      @posts = Post.where("category_id = ? and institution_id = ?", category, @institution).order("created_at DESC")
    end
    authorize! :read, @post
    respond_with(@posts)
  end

Can someone please point me in the right direction?

EDIT 2: My view (index.html.haml)

%h1 Listing posts

%table
  %tr
    %th Title
    %th Description
    %th User
    %th Category
    %th Type
    %th Class
    %th Institution

  - @posts.each do |post|
    %tr
      %td= post.title
      %td= post.description
      %td= post.user_id
      %td= post.category_id
      %td= post.institution_id

Answer 1

You are overwriting @posts with each iteration.
Try this:

def index
    @institution = Institution.find(current_user.institution.id)
    @categories = Category.all
    @posts = []
    @categories.each do |category|
      tposts = Post.where("category_id = ? and institution_id = ?", category, @institution).order("created_at DESC")
      @posts += tposts if tposts
    end
    authorize! :read, @post
    respond_with(@posts)
end

To retrieve all posts with non null category_id, try this:

def index
    @institution = Institution.find(current_user.institution.id)
    @categories = Category.all
    @posts = Post.where("category_id is not null and institution_id = ?", @institution).order("created_at DESC")
    authorize! :read, @post
    respond_with(@posts)
end

Change is not null to > 0 for integer category_id or != '' if your table contains ” instead of nulls.

Good luck.