Loop within Loop in Rails Controller

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

why dont you just query for all posts via Post.all or do you only want posts that have a category_id set? — cpjolicoeur
– cpjolicoeur, Commented Jun 5, 2012 at 19:51
If I'm not mistaken you simply want to group your posts by category, see Rails Guides — topek
– topek, Commented Jun 5, 2012 at 19:53
I forgot to mention that I want to retrieve posts that have a category_id set! Sorry. — Daniel Garzon
– Daniel Garzon, Commented Jun 5, 2012 at 19:54

Anil · Accepted Answer · 2012-06-05 21:02:21Z

6

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.

edited Jun 5, 2012 at 21:02

answered Jun 5, 2012 at 20:00

Anil

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5 Comments

Daniel Garzon Over a year ago

Doesn't seem to work in my case. I just want to loop each category and use my retrieval as I tested it and it works.

Daniel Garzon Over a year ago

Thank you for your quick answer Anil! You are right I checked my console and I was overwriting @posts, but I followed your advise and the '<<' is giving me an error: "undefined method `<<' for nil:NilClass". Are you sure those are valid brackets?

Anil Over a year ago

@DanieGarzon Give it another try.

Daniel Garzon Over a year ago

Awesome! I am getting closer. In the console I am getting the desired results for @posts but because they are now grouped into different arrays,depending on the category, I am getting errors in my view: "undefined method `title'" although each post have their own title. Can you please check my original post? I did an edit to show my view.

Daniel Garzon Over a year ago

I have no words to thank you! It worked, actually I had to add += to the stuffer. Update your answer please, and I already gave you the up! Thank you once again..

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