title: Ruby one line if return statement
body: <p>is there a way to shorten this line on Ruby?</p>
  
  <pre><code>if (res = bla_permission_invalid).is_a? String then return res end
  </code></pre>
  
  <p>on</p>
  
  <pre><code>def something # many things that like this
    if (res = bla_permission_invalid).is_a? String then return res end
    # do something else
    return true
  end
  </code></pre>
  
  <p>when the content of bla_permission_invalid are something like</p>
  
  <pre><code>def bla_permission_invalid
    return invalid_address_report_func if invalid_address?
    return permission_error_report_func if @user.not_one_of? [ :group1, :group2 ]
    return nil
  end
  </code></pre>
  
  <p><code>invalid_adress_report_func</code> and <code>permission_error_report_func</code> returns string</p>