How to make sure that freelancer does not take your code?

Hi,
I am about to hire a freelancer coder. How to make sure that freelancer does not take your code?

Couple of options that I can think of:

• Ask him/her to sign an intellectual property document.
• Hire couple of freelancers and give each one just a part of an app, so that neither of freelancers would have full app.

What can you offer? :)

Thanks