Rails - How to export nested resources to CSV in Rails?

Question

I am trying to export some data to CSV in Rails 4. I have two models: Excursions and Inscriptions. One excursion has many inscriptions and one inscription belongs to one excursion.

I have my nested routes defined this way:

  resources :excursions do
    resources :inscriptions
    get 'exportcsv' => 'excursions#download'
  end

So the behavior I am trying to achieve is: when I visit the route /excursions/1/exportcsv, a CSV will be downloaded to my computer and it will contain all the inscriptions with excursion_id = 1 in CSV format.

In my excursion model I have defined self.to_csv:

  def self.to_csv(options = {})
    CSV.generate(options) do |csv|
      csv << column_names
      self.inscriptions.each do |inscription|
        csv << inscription.attributes.values_at(*column_names)
      end
    end
  end

And my excursion controller's method download:

  def download
    @excursion = Excursion.find(params[:id])
    respond_to do |format|
      format.html
      format.csv { send_data @excursion.to_csv }
    end
  end

EDIT: When I go to a route like: /excursions/:id/exportcsv the server is throwing an ActiveRecord::RecordNotFound error. This error is easy to solve, but if I solve the RecordNotFound I get an ActionController::UnknownFormat in this line:

  def download
    @excursion = Excursion.find(params[:id])
    respond_to do |format|  ########THIS LINE
      format.html
      format.csv { send_data @excursion.to_csv }
    end
  end

What I am doing wrong? Maybe all this approach is not correct...

What is the issue? What is the output of your CSV? Are you having issue with the csv header columns or something else? — Dharam Gollapudi, Mar 09 '16 at 21:56

Dharam Gollapudi · Accepted Answer · 2016-03-09T22:19:35.997

0

I would update the routes to the following:

resources :excursions do
  get 'download', on: :member, constraints: { format: /(html|csv)/ }
  resources :inscriptions
end

Also there is a bug in your model code. You are exporting inscriptions but are using Excursion column_names instead of Inscription column_names. Following is the updated model code.

class Excursion < ActiveRecord::Base
  def to_csv(options = {})
    CSV.generate(options) do |csv|
    inscription_column_names = Inscription.column_names

    csv << inscription_column_names

    self.inscriptions.each do |inscription|
      csv << inscription.attributes.values_at(*inscription_column_names)
    end
  end
end

Now try to access http://localhost:3000/excursions/:id/download.csv

Replace :id with an existing Excursion records id. If you still encounter ActiveRecord::RecordNotFound error, then the problem could be that you are trying to access an Excursion that doesn't actually exist in the database.

edited Mar 09 '16 at 22:19

answered Mar 09 '16 at 22:08

Dharam Gollapudi

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I have updated the code but now the servers is throwing an: *Missing template excursions/download, application/download with {:locale=>[:en], :formats=>[:html], :variants=>[], :handlers=>[:erb, :builder, :raw, :ruby, :coffee, :jbuilder]}.* – F404 Mar 09 '16 at 22:14
1

Ok, I was missing the .csv extension. Anyway, now the server says that there is no method named to_csv: `undefined method 'to_csv' for # Did you mean? to_s` – F404 Mar 09 '16 at 22:17
Convert the class method `to_csv` to instance method `to_csv`. Updated the answer. – Dharam Gollapudi Mar 09 '16 at 22:20
Ups, sorry! My fault :) – F404 Mar 09 '16 at 22:44

Rails - How to export nested resources to CSV in Rails?

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