[Ruby on Rails] CSV output function

Target

Development environment

ruby 2.5.7 Rails 5.2.4.3 OS: macOS Catalina

Premise

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-Build login environment with devise -Posting function that only logged-in users can do -Post editing function (update, delete)

The post model has title and body columns The user model has an N: 1 relationship.

First, write the completed code, and then write the supplementary code.

Completion code

Editing controller

app/controllers/posts_controller.rb

class PostsController < ApplicationController
  require 'csv'

  def new
    @post = Post.new
    @posts = Post.all
    respond_to do |format|
      format.html
      format.csv do |csv|
        send_posts_csv(@posts)
      end
    end
  end

  private
  def send_posts_csv(posts)
    csv_data = CSV.generate do |csv|
      column_names = %w(Name of contributor Title Body)
      csv << column_names
      posts.each do |post|
        column_values = [
          post.user.name,
          post.title,
          post.body,
        ]
        csv << column_values
      end
    end
    send_data(csv_data, filename: "Post list.csv")
  end
end

view

erb:app/views/posts/new.html.erb

<%= link_to "Output with csv",new_post_path(format: :csv) %>

Supplementary code

controller

app/controllers/posts_controller.rb

class PostsController < ApplicationController
  require 'csv' #← Be careful because it is easy to forget

  def new
    @post = Post.new
    @posts = Post.all
    # respond_to is a method that performs processing according to the request.
    #Normally, html is requested, so the process is not described.
    #view link_Since format is specified as csv with to,
    #Press the link to send_posts_csv(@posts)Is processed.
    respond_to do |format|
      format.html
      format.csv do |csv|
        send_posts_csv(@posts)
      end
    end
  end

  private
  def send_posts_csv(posts)
    # CSV.generate is a type of CSV library that automatically converts the target data into CSV format.
    csv_data = CSV.generate do |csv|
      # %w()Returns an array separated by whitespace
      column_names = %w(Name of contributor Title Body)
      # csv << column_names defines the names that go into the columns of the table.
      csv << column_names
      # column_Defines the column values to assign to values.
      posts.each do |post|
        column_values = [
          post.user.name,
          post.title,
          post.body,
				]
      # csv << column_valuesh defines the values that go into the rows of the table.
        csv << column_values
      end
    end
    #Defines the filename of the csv output.
    send_data(csv_data, filename: "Post list.csv")
  end
end

view

erb:app/views/posts/new.html.erb

<!--Specify format as csv and respond to controller_Execute to processing-->
<%= link_to "Output with csv",new_post_path(format: :csv) %>