How to pass parameters between New and Create actions?

I have a parameter in my url when linking to the Ne开发者_StackOverflow社区w action. I need this parameter in the create action. How do you do it?

---

You may use a hidden field.

<input id="thing" type="hidden" value="<%= params[:thing] %>" />

Put that code in the new view.

---

I've found that <input type="hidden" name="modal" value="true" /> also works.