Ryan Blakely

Thanks so much for the help Chris. I'm going to spend some time reviewing all of this but I was able to get it to work with the final code bit you shared.

Here is my current (now working) rake file for those also looking for the solution :

require 'csv'
require 'open-uri'
namespace :post_import do
  desc "Import posts daily"
  task posts: :environment do
    filename = File.join Rails.root, "posts.csv"
    counter = 0

    CSV.foreach(filename) do |row|
      name, category_ids, description = row
      post = Post.new(name: name, description: description) if post == nil
      post.save 

      #separate string of category ids into array
      a_categories = category_ids.split(",")

      a_categories.each do |category_id|
        post.styles.where(category_id: category_id).first_or_create
      end

      counter += 1 if post.persisted?
    end

    puts "Imported #{counter} [posts]
  end
end

I am able to split the ids into an array successfully - but somewhere in

categories = Category.where(id: category_ids)
post.categories = categories

the output becomes quadruplicated and I dont understand why. I am using a csv with only one row of data for testing. Even when I remove multiple category ids and leave a single id, the output of post.categories is [1,1,1,1]. I dont think this is what you mean by idemoptent as this is a single csv imported once.

here is the code that I am using for my rake due to my particular schema:

a_categories = category_ids.split(",")
categories = Style.where(category_id: a_categories)
post.styles = categories

Is there anything here that could cause the quadruplication?

Thanks Chris, I have the join table created though my naming convention is not the most logical - I've called it styles rather than PostCategories.

My csv formats the categories by ID. For example a row would look like "1,2,3" with 1, 2, 3 representing the category_ids of three unique categories. Can you give me an example of how to split them up and "do a Category.find() on them to grab the categories"?

Here is what I have in my rake task:

require 'csv'
require 'open-uri'
namespace :post_import do
  desc "Import posts daily"
  task posts: :environment do
    filename = File.join Rails.root, "posts.csv"
    counter = 0

    CSV.foreach(filename) do |row|
      name, category, description = row
      post = Post.create(name: name, description: description)
      post.styles.build(category_id: category)

      counter += 1 if post.persisted?
    end

    puts "Imported #{counter} [posts]"
  end
end

This works, but only for the first category in the row. Categories 2 and 3 arent being assigned.

Thanks Nick and Andrew! I've been using the videos for a little while but excited to participate in the community now!
Andrew - I'm running a half-marathon in February as well! (Phoenix marathon). Best of luck with your training! I plan on starting a fairly light 12 week training program just after thanksgiving, let me know if you'd like me to send you a copy!

I am building a rails application that associates posts with many different categories. For example, I have a Post and need to be able to assign it to the categories Sports, News and Science through csv import via rake task.

My question is how can I import an array of multiple category_ids into my Post model? I have it working where I can manually create a new Post and assign multiple categories to the post, but I am confused as to how to complete this through csv. I need help figuring out the best way to accomplish this.

Here is what I have so far:

Schema

  create_table "posts", force: :cascade do |t|
    t.string   "name"
    t.text     "description"
  end

  create_table "styles", force: :cascade do |t|
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
    t.integer  "post_id"
    t.integer  "category_id"
  end

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

Post.rb

class Post < ApplicationRecord  
  has_many :styles
  has_many :categories, through: :styles
end

Category.rb

class Category < ApplicationRecord
  has_many :styles
  has_many :posts, through: :styles
end

Style.rb

class Style < ApplicationRecord
  belongs_to :post
  belongs_to :category
end

Rake Task

require 'csv'
require 'open-uri'
namespace :post_import do
  desc "Import posts daily"
  task posts: :environment do
    filename = File.join Rails.root, "posts.csv"
    counter = 0

    CSV.foreach(filename) do |row|
      name, category, description = row
      post = Post.create(name: name, category_ids: category, description: description)
      counter += 1 if post.persisted?
    end

    puts "Imported #{counter} [posts]"
  end
end

Ryan Blakely. I'm a PHX, Arizona based Rails developer. I started learning Rails about 2 years ago during my senior year of college at Arizona State University. After graduating and working for a year as an Industrial Engineer, I decided to leave my job to focus on coding full time. I started a web development shop called Open-Labs and build sites for local clients to pay the bills. In my free time I make tutorials on how to build rails apps and share what I am learning on my youtube channel. A few side projects I am currently working on include Vihbe and Open-Rails.

When I'm not coding I enjoy traveling, hiking, running, photography, art and yoga.

I'm excited to be a part of this great community Chris has created and hope to meet others like me. Please feel free to say hello!