title: Rails Associations - Do I need has many and also belongs to together
body: <p>If I have a class Category and a class Post, post belongs to a category then I make a <code>t.belongs_to</code> in Post migration, but do I have to necessarily declare a <code>t.has_many</code> in Category? If not, if I have to use just one, which is the best to choose?</p>