How to restrict user to choose 1 category for a post

Question

I wish to restrict the user posting a new article to select only 1 category for that post. It doesn't matter which category he chooses as long as he chooses just one. This way posts are maintained under a hierarchy (and I want to avoid users clicking all categories so that their posts appear everywhere).

I don't want to restrict the user to a specific category, I just want to limit the number of categories the user can choose for a post to 1.

Is there any way to achieve this in Wordpress?

Answer 1

I've solved this in the past for a client by using remove_meta_box to hide the default categories meta box, then adding my own meta box via add_meta_box which outputs categories as a drop-down select list, which effectively limits selection to a single item.