Display all posts from a certain category

Question

I'm looking to display all posts from a certain category on a page, I currently have Posts & Category models linked by a HABTM relationship. I want to be able to click the link on my index.html.erb and go through to a page that lists all the posts which belong to that certain category.

Do I need to create a controller for category and new routes?

Post.rb

class Post < ActiveRecord::Base
  has_and_belongs_to_many :categories
  belongs_to :user
end

Category.rb

class Category < ActiveRecord::Base
  has_and_belongs_to_many :posts
end

Index.html.erb (My current way to display the category for each post)

<% post.categories.each do |category| %>
  <% category.posts.each do |post| %>
    <%= link_to category.name, post_url(post) %>
  <% end %>
<% end %>

** Update **

After Answer routes have been produced as below.

          category_posts GET    /categories/:category_id/posts(.:format)          posts#index
                     POST   /categories/:category_id/posts(.:format)          posts#create
   new_category_post GET    /categories/:category_id/posts/new(.:format)      posts#new
  edit_category_post GET    /categories/:category_id/posts/:id/edit(.:format) posts#edit
       category_post GET    /categories/:category_id/posts/:id(.:format)      posts#show
                     PATCH  /categories/:category_id/posts/:id(.:format)      posts#update
                     PUT    /categories/:category_id/posts/:id(.:format)      posts#update
                     DELETE /categories/:category_id/posts/:id(.:format)      posts#destroy
          categories GET    /categories(.:format)                             categories#index
                     POST   /categories(.:format)                             categories#create
        new_category GET    /categories/new(.:format)                         categories#new
       edit_category GET    /categories/:id/edit(.:format)                    categories#edit
            category GET    /categories/:id(.:format)                         categories#show
                     PATCH  /categories/:id(.:format)                         categories#update
                     PUT    /categories/:id(.:format)                         categories#update
                     DELETE /categories/:id(.:format)                         categories#destroy

Klaus · Answer 1 · 2015-03-28T16:52:18.787

1

Have to do it as answer:

In your Category model:

def to_param
  name
end

But please accept Logan's anwer as the correct one, because he solves your original problem.

edited Mar 28 '15 at 16:52

answered Mar 28 '15 at 16:48

Klaus

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How would I display the link to the category in my view? – Jonathan Mar 28 '15 at 16:50
A bit confusing with the comments and answers. Okay, did you follow Logan's suggestions? What ist the result of `rake routes`? – Klaus Mar 28 '15 at 16:54
Added Routes to the Question – Jonathan Mar 28 '15 at 16:56
Okay, sorry, my fault: It must be `<%= link_to category.name, category_posts_path %>` – Klaus Mar 28 '15 at 16:58
No route matches {:action=>"index", :controller=>"posts"} missing required keys: [:category_id] Getting this error for some reason. – Jonathan Mar 28 '15 at 16:59
Oh wait... I just noticed that you want to have the category shown.. `<%= link_to category.name, category_path %>` – Klaus Mar 28 '15 at 17:07
<%= link_to category.name, category_path(category.name) %> This worked. Thanks – Jonathan Mar 28 '15 at 17:11

score 0 · Accepted Answer · answered Mar 28 '15 at 16:27

0

You can nest posts inside categories

resources :categories do
  resources :posts
end

This will make routes like categories/1/posts and URL helpers like category_posts_path(1) where 1 is the category ID. Then in your posts controller, you will have params[:category_id] available which can lookup the category and then fetch the posts. Something like

if params[:category_id]
  @category = Category.find params[:category_id]
  @posts = @category.posts
else
  @posts = Post.all
end

answered Mar 28 '15 at 16:27

Logan Serman

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Thanks Logan for the detailed answer! How would I go about linking to the category in my index view? Also is there anyway to change the URL to be the name attribute instead of the id? – Jonathan Mar 28 '15 at 16:30
Run `rake routes` to see your possible routes. With Logans explanation you will have categories_post_path which will lead you to a specific category. You can use to_param to make the name of the category to a parameter. – Klaus Mar 28 '15 at 16:36
Thanks Klausinho - appreciated! – Jonathan Mar 28 '15 at 16:38
@klausinho How would I go about doing the to_param? – Jonathan Mar 28 '15 at 16:44
@klausinho Currently getting **undefined local variable or method `categories_post_path'** from putting **<%= link_to category.name, categories_post_path %>** – Jonathan Mar 28 '15 at 16:47
I mentioned the correct path helper in my post, `category_posts_path()`. `categories_post_path` is incorrect. – Logan Serman Mar 28 '15 at 19:11

score 0 · Answer 3 · answered Jun 25 '20 at 20:12

0

def index 
 if params[:category_id]
  @posts = Post.where("category_id = ?", params[:category_id])
 else
   @posts = Post.all
 end 
end

An alternative to Logan's Answer as in some cases it might not work.

answered Jun 25 '20 at 20:12

Aditya Joardar

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Display all posts from a certain category

3 Answers3