title: Regex to validate string having only characters (not special characters), blank spaces and numbers
body: <p>I am using Ruby on Rails 3.0.9 and I would like to validate a string that can have only characters (not special characters - case insensitive), blank spaces and numbers.</p>
  
  <p>In my validation code I have:</p>
  
  <pre><code>validates :name,
    :presence   =&gt; true,
    :format     =&gt; { :with =&gt; regex } # Here I should set the 'regex'
  </code></pre>
  
  <p>How I should state the regex?</p>