Validation of uploaded Excel file before save using Rails with Roo-xls gem

问题

In a model, before uploading an .xls file, I want to be able to validate excel files before they are saved by the application. I am trying to open the to-be-saved excel file from the :file_url object(column in comits table where the .xls files will be saved) and then validate it but I am getting a no implicit conversion of Symbol into String error.

The validation works when I place the actual file path of an excel file that has been uploaded and saved by carrierwave into Roo::Excel.new("") but that defeats the purpose of my validation.

How can I grab the excel file without it being stored in the application?

I appreciate the help! I hope is not too confusing.

This is my comit.rb

class Comit < ActiveRecord::Base
  belongs_to :user
  mount_uploader :file_url, ComitUploader, mount_on: :file_url
  validates :filename, :file_url, presence: true
  validates_format_of :file_url, with: /.xls/, message: "Wrong file format"
  before_save :validate_excel

  def validate_excel
    sheet = Roo::Excel.new(:file_url)
    errors = []

    header = sheet.row(1)
    num_of_columns = sheet.last_column

    errors << 'Need headers' unless
    errors << 'Need more columns' if num_of_columns < 21

    errors
  end
end

回答1:

You're passing the symbol :file_url to Roo::Excel.new, it wants a path to the file. Try:

sheet = Roo::Excel.new(file_url)

回答2:

You can send the tempfile to Roo.
Let's say you are sending the file to params as :file:

Roo::Excel.open(params[:file].tempfile.to_path.to_s)

回答3:

Okay, I figured it out. Instead of Roo::Excell, it needs to be

sheet = Roo::Spreadsheet.open(self.file_url)

Also, I needed to install the gem 'roo-xls' gem in order to read the spreadsheet.

回答4:

In my case following code is working fine. (Assuming that you have installed required gems)In my case I have the .xls file in my root directory

require 'roo'
require 'roo-xls'
class ExcelReader
  def read_file()
  sheet = Roo::Spreadsheet.open('Test.xls')
  sheet.each do |row|
  puts row
end
 end
  obj=ExcelReader.new()
  obj.read_file()
 end

来源：https://stackoverflow.com/questions/31573319/validation-of-uploaded-excel-file-before-save-using-rails-with-roo-xls-gem