ruby - Loop within Loop in Rails Controller -

i trying retrieve database posts , list them in desc order respect creation date. far have managed test posts belong 1 category want display posts no matter category belong to. know have loop trough each category, , posts each dont know how to. here code:

edit:

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

can please point me in right direction?

edit 2: 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 |post|     %tr       %td= post.title       %td= post.description       %td= post.user_id       %td= post.category_id       %td= post.institution_id 

you overwriting @posts each iteration. try this:

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

to retrieve posts non null category_id, try this:

def index     @institution = institution.find(current_user.institution.id)     @categories = category.all     @posts = post.where("category_id not null , institution_id = ?", @institution).order("created_at desc")     authorize! :read, @post     respond_with(@posts) end 

change is not null > 0 integer category_id or != '' if table contains '' instead of nulls.

good luck.