title: Symfony2: Processing form with relational doctrine data
body: <p>I'm building simple CMS in S2 and I have little trouble wih processing relational Category in Article form.</p>
  
  <p>Code for CategoryType and action: <a href="http://codepaste.net/ahyoig" rel="nofollow">http://codepaste.net/ahyoig</a> all like in tutorial/manual on Symfony site.</p>
  
  <p>Form looks fine, but when i process data (also like in manual) i get error: "Expected argument of type array, string given" in select field and I ahve no idea right now how to solve it.</p>