Ruby-Rails Spreadsheet "corrupted" under Microsoft Excel 2010 - ruby-on-rails

Question

I am using Spreadsheet gem to allow users to export data with .xls format. The code I am showing is allowing users to open the file in Open Office and MS Excel for MAC, but not for Windows, which I get a "file is corrupted" error.
I have a method that do the XLS export like this:
book = Spreadsheet::Workbook.new
sheet1 = book.create_worksheet(:name => "Expired Activity")
# Title
title_format = Spreadsheet::Format.new(:size => 12, :pattern => 1, :pattern_fg_color => :blue, :align => :merge)
for i in 0..5
sheet1.row(0).set_format(i, title_format)
end
sheet1.row(0).push "Activity"
# Header row
header_format = Spreadsheet::Format.new(:size => 11, :pattern => 1, :pattern_fg_color => :yellow, :align => :merge)
index_row = sheet1.row(1)
index_row.push("Date")
index_row.push("First Name")
index_row.push("Last Name")
for i in 0..2
index_row.set_format(i, header_format)
end
# Row values
row_iterator = 2
#expired.each do |expired|
sheet1.row(row_iterator).push(expired.earnedOn, expired.firstName, expired.lastName)
row_iterator = row_iterator + 1
end
file_io = StringIO.new
book.write file_io
file_io.string
And this method is being called like this:
format.xls {#expired = current_user.recent_activity(unlimited_size,params[:start],nil);
send_data(build_excel_expired_activity, :filename => "#{Time.now.strftime('%Y-%m-%d')}_Expired_Activity.xls", :type => "application/xls", :disposition => 'attachment')
}
Any thoughts, or ideas?

Answer 1

You might want to have a look at the axlsx gem and its rails counterpart acts_as_xlsx. It supports full schema validation so you don't have to fight with this kind of thing.
https://www.ruby-toolbox.com/projects/axlsx