Bayonet gem

Bayonet is a Microsoft Excel write-only gem that reads and produces XLSX files. It's strength lies in the fact that it's able to open bigger Excel files (even with macros!) -- and write cells without touching the rest of the Excel file. I've written the gem because roo was unbearably slow and was using ~1GB of RAM to read a 5MB XLSX file.

WARNING: Use this gem at your own risk. It's writing directly to sheet XML files and uses a few tricks that Microsoft Excel 2010 seems to be fine with, but I cannot guarantee that future (or past) versions will play along. That being said, I've used it successfully in one of my projects. If you find any bugs, let me know.

workbook = Bayonet::Workbook.new(a_file_path)

workbook.on_sheet('The First Sheet') do |sheet|
  sheet.set_typed_cell('A', 1, "I'm a string") # set a cell auto-typed to a string
  sheet.set_typed_cell('B', 1, 42)             # set a cell auto-typed to a number
  sheet.set_cell('C', 1, "Some value")         # set a cell without setting its type
  sheet.write_string('D', 1, "Some value")     # set a cell and forcing it to be a string
  sheet.write_number('E', 1, 23)               # set a cell and forcing it to be a number
end

workbook.write_and_close(output_file_path)

See the Tips section for more information.

• If you want to modify an existing, possibly huge XLSX file.
• If other gems fail at the task or are too slow.

• If you want to create an XLSX file from scratch.
• If you plan to open legacy (binary) XLS files.
• If your XLSX file is small and other gems are working fine.

Other gems I can recommend are:

• roo (read/write, lots of features and supported formats)
• axlsx (write-only)
• creek (read-only, very fast)

Normally you should use set_typed_cell, which sets the cell type correctly and falls back to string. If you're using a prepared XLSX sheet you might not want to override the current cell type. You should use set_cell for those instances. If you want to force a cell type, you can use write_string or write_number instead, but this should rarely be necessary.

It's simply not been implemented yet. I've been writing to template files with pre-defined cells to fill, so reading cells was not necessary. It shouldn't be hard to implement, though there might be some edge cases I haven't considered yet, that's why I left it out for now. Pull requests are welcome, otherwise I'd suggest to use other gems for that.