title: Axlsx Ruby Gem - Creating a dropdown with custom values
body: <p>I'm using <a href="https://github.com/randym/axlsx" rel="nofollow noreferrer">axlsx</a> gem to export data into excel from Ruby/Rails. </p>
  
  <p>I need to add a dropdown with custom values - value1, value2, value3 etc. The following is the code I tried</p>
  
  <pre><code>excel = Axlsx::Package.new
  wb = excel.workbook
  
  wb.add_worksheet(name: "sample_sheet") do |sheet|
    sheet.add_data_validation("A1:A100", {
        :type =&gt; :list,
        :formula1 =&gt; "value1 value2 value3",
        :showDropDown =&gt; false,
        :showErrorMessage =&gt; true,
        :errorTitle =&gt; '',
        :error =&gt; 'Please use the dropdown selector to choose the value',
        :errorStyle =&gt; :stop,
        :showInputMessage =&gt; true,
        :prompt =&gt; 'Choose the value from the dropdown'
    })
  end
  
  excel.serialize('sample_excel.xlsx')
  </code></pre>
  
  <p>The code creates the excel but when I open it I get this excel error <a href="https://github.com/randym/axlsx" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Dg72O.png" alt="excel error"></a> 
  The values are not added to the dropdown.</p>
  
  <p>Alternatively,</p>
  
  <pre><code>:formula1 =&gt; "B1:B2"
  </code></pre>
  
  <p>works fine, it adds the contents of B1 and B2 to the dropdown. In my use-case I need custom values to be added, they are not stored in the excel sheet.</p>
  
  <p>What is the correct way to add custom values in data validation dropdown? Kindly help.</p>