Rails - display category name on views via relationship tables

Question

I have two tables that I put relationship with blog and post_categories. Below is the schema:

  create_table "blogs", force: :cascade do |t|
    t.string "title"
    t.text "body"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "slug"
    t.integer "status", default: 0
    t.bigint "post_category_id"
    t.index ["post_category_id"], name: "index_blogs_on_post_category_id"
    t.index ["slug"], name: "index_blogs_on_slug", unique: true
  end

  create_table "post_categories", force: :cascade do |t|
    t.string "name"
    t.text "description"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

Now what I am trying to do is to display the category name instead of category id on my blog index.html.erb file. I did the following but did not work:

<tbody>
    <% @blogs.each do |blog| %>
      <tr>
        <td><%= blog.title %></td>
        <td><%= blog.body %></td>
        <% PostCategory.all.each do |c| %>
          <% if c.id == blog.post_category %>
          <td><%= c.name %>
          <% end %>
        <td><%= link_to 'Show', blog %></td>
        <td><%= link_to 'Edit', edit_blog_path(blog) %></td>
        <td><%= link_to 'Destroy', blog, method: :delete, data: { confirm: 'Are you sure?' } %></td>
      </tr>
    <% end %>
  </tbody>

Note: I also tried accessing it directly via <td><%= blog.post_category.name %></td>but did not work still.

Any idea how can I display the category name instead of category id associated?

If I used this <td><%= blog.post_category %></td> it gives me something like this: #<PostCategory:0x007fafd058f070> — user6398538
– user6398538, Commented Jan 2, 2019 at 6:17

ray · Accepted Answer · 2019-01-02 06:25:45Z

1

As per you schema provided, it is noted that PostCategory object has many Blog objects

model changes,

class PostCategory < ApplicationRecord
  has_many :blogs
end

class Blog < ApplicationRecord
  belongs_to :post_category
end

view changes,

<tbody>
  <% @blogs.each do |blog| %>
    <tr>
      <td><%= blog.title %></td>
      <td><%= blog.body %></td>
      <td><%= blog.post_category.name rescue 'No post category present for this blog' %></td>
      <td><%= link_to 'Show', blog %></td>
      <td><%= link_to 'Edit', edit_blog_path(blog) %></td>
      <td><%= link_to 'Destroy', blog, method: :delete, data: { confirm: 'Are you sure?'} %></td>
    </tr>
  <% end %>

edited Jan 2, 2019 at 6:25

answered Jan 2, 2019 at 6:16

ray

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11 Comments

user6398538 Over a year ago

RAY Tried this already but got undefined method `name' for nil:NilClass

ray Over a year ago

updated answer, it is your data problem as association and schema is proper but you do not have data as per association. use of try method can handle issue

ray Over a year ago

@MarcSolva for blog.post_category_id, there must be id present in table post_categories

user6398538 Over a year ago

It works but is it safe to just let "try" method handle the work? is this a good practice? Also can explain the association issue more?

user6398538 Over a year ago

RAY - do i need to add a migration id for the post_categories table to solve this issue?

|

Cryptex Technologies · Accepted Answer · 2019-01-02 06:36:59Z

0

model changes,

class PostCategory < ApplicationRecord
  has_many :blogs
end

class Blog < ApplicationRecord
  belongs_to :post_category
end

view changes,

<tbody>
  <% @blogs.each do |blog| %>
    <tr>
      <td><%= blog.title %></td>
      <td><%= blog.body %></td>
      <td><%= blog.post_category.try(:name) %></td>
      <td><%= link_to 'Show', blog %></td>
      <td><%= link_to 'Edit', edit_blog_path(blog) %></td>
      <td><%= link_to 'Destroy', blog, method: :delete, data: { confirm: 'Are you sure?'} %></td>
    </tr>
  <% end %>

edited Jan 2, 2019 at 6:36

answered Jan 2, 2019 at 5:40

Cryptex Technologies

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10 Comments

user6398538 Over a year ago

PG::UndefinedColumn: ERROR: column post_categories.blog_id does not exist LINE 1: ... "post_categories".* FROM "post_categories" WHERE "post_cate...

Cryptex Technologies Over a year ago

First reset your database and start creating

Cryptex Technologies Over a year ago

Why you are calling post_categories.blog_id

ray Over a year ago

Downvoted! blog belongs_to :post_category as blogs table have foregin key post_category_id

user6398538 Over a year ago

belongs_to :post_category as blogs place this on my blog model but I got this: compile error # GET /blogs.json def index @blogs = Blog.all end def post_category_0

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