gistfile1.rb

def show_modal
  NSApp.beginSheet(@my_modal_window,
                   modalForWindow: @my_main_window,
                   modalDelegate: self,
                   didEndSelector:nil,
                   contextInfo:nil)
end

def cancel_modal(sender)
  NSApp.endSheet(@my_modal_window)
  @my_modal_window.orderOut(sender)
end

def submit_modal_form(sender)
  value = @my_value_text_field.stringValue
  NSApp.endSheet(@my_modal_window)
  @my_modal_window.orderOut(sender)
  #do something with value
end