title: undefined method `symbolize_keys!' for #<Array rails 4
body: <p>In <code>mcs_mailer.rb</code>:</p>
  
  <pre><code> def invite(email,subject,body,attachment_urls)
  
   @attachment_urls= attachment_urls
  
   mandrill_mail(
    template: 'group-invite',
    subject: subject,
    to: email,
    html: body,
    attachments: [ @attachment_urls.each do |url|
                  {
                    content: File.read(url),
                    name: 'offer.pdf',
                    type: 'application/pdf'
                  }
                end
                ])
  </code></pre>
  
  <p>I am using <code>mandrill_mail</code> in my rails application.I want to send mail with multiple attachments. But getting error in the each loop <code>undefined method</code>symbolize_keys!' for #