title: How to process text input data before form submit ruby on rails
body: <p>I'm using rails form helper to generate form and retrieve data from users.
  like this</p>
  
  <pre><code>&lt;div class="controls"&gt;
    &lt;%= f.text_field :duration, class: "input-large" %&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>however,I need this input, before its store to database 'duration' column,multiply by 10.
  I have search about this and try implement a method,create a function,which multiply the value,and call it under before_save</p>
  
  <pre><code>before_save  :multiply_ten, on: [ :create,:update ]
  </code></pre>
  
  <p>problem is,i'm not only updating this column using web page form,and also by http request send by device.by implementing this I multiply all value by 10,But I only want the web form input part multiply 10.
  is there a way to do it in form css or have other tricks?
  thanks</p>