Rails csv导入与关联

Question

我正在构建一个rails应用程序，它将帖子与许多不同类别相关联。 例如，我有一个帖子，需要能够通过rake任务通过csv导入将它分配到体育，新闻和科学类别。

我的问题是如何将多个category_ids数组导入到Post模型中？ 我有它的工作，我可以手动创建一个新的帖子，并为帖子分配多个类别，但我很困惑如何通过csv完成这一点。 我需要帮助找出实现这一目标的最佳方法。

这是我到目前为止：

架构

  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

耙任务

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

Answer 1

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

      #you can user find or create, but for clarity I split it
      post = Post.where(name: name).first
      post = Post.new(name: name, description: description) if post == nil

      #now we can simply add the style which joins to the category
      post.styles.build(category_id: category)
      post.save
      counter += 1 if post.persisted?
    end

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

Answer 2

我能够在gorails.com的Chris的帮助下解决这个问题。 这是我的（粗略）工作解决方案。 希望这可以帮助其他人解决这个问题！

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