Ruby on Rails: Validate CSV file - ruby-on-rails

Question

Having followed the RailsCast on importing CSV (http://railscasts.com/episodes/396-importing-csv-and-excel), I am trying to validate that the file being uploaded is a CSV file.
I have used the gem csv_validator to do so, as documented here https://github.com/mattfordham/csv_validator
And so my model looks like this:
class Contact < ActiveRecord::Base
belongs_to :user
attr_accessor :my_csv_file
validates :my_csv_file, :csv => true
def self.to_csv(options = {})
CSV.generate(options) do |csv|
csv << column_names
all.each do |contact|
csv << contact.attributes.values_at(*column_names)
end
end
end
def self.import(file, user)
allowed_attributes = ["firstname","surname","email","user_id","created_at","updated_at", "title"]
CSV.foreach(file.path, headers: true) do |row|
contact = find_by_email_and_user_id(row["email"], user) || new
contact.user_id = user
contact.attributes = row.to_hash.select { |k,v| allowed_attributes.include? k }
contact.save!
end
end
end
But my system still allows me to select to import non-CSV files (such as .xls), and I receive the resulting error: invalid byte sequence in UTF-8.
Can someone please tell me why and how to resolve this?
Please note that I am using Rails 4.2.6

Answer 1

You can create a new class, let's say ContactCsvRowValidator:
class ContactCsvRowValidator
def initialize(row)
#row = row.with_indifferent_access # allows you to use either row[:a] and row['a']
#errors = []
end
def validate_fields
if #row['firstname'].blank?
#errors << 'Firstname cannot be empty'
end
# etc.
end
def errors
#errors.join('. ')
end
end
And then use it like this:
# contact.rb
def self.import(file, user)
allowed_attributes = ["firstname","surname","email","user_id","created_at","updated_at", "title"]
if file.path.split('.').last.to_s.downcase != 'csv'
some_method_which_handle_the_fact_the_file_is_not_csv!
end
CSV.foreach(file.path, headers: true) do |row|
row_validator = ContactCsvRowValidator.new(row)
errors = row_validator.errors
if errors.present?
some_method_to_handle_invaid_row!(row)
return
end
# other logic
end
end
This pattern can easily be modified to fit your needs. For example, if you need to have import on several different models, you could create a base CsvRowValidator to provide basic methods such as validate_fields, initialize and errors. Then, you could create a class inheriting from this CsvRowValidator for each model you want, having its own validations implemented.