You could do this as well:

  Repo.insert! %Post{title: "Awesome Post", slug: "awesome-post", category_id: 3}

If you don't need flexibility. Well, usually that's bad idea - you'd want to carefully handle what's can be mass-assigned and what should be carefully set by hand. In case of ecto, you'd do:

  %Post{user_id: current_user.id}
  |> Post.changeset(attributes)
  |> Repo.insert

In case of rails/AR you'll use strong params (or alternatives)

  Post.create(post_params.merge(user_id: current_user.id))

  def post_params
    params.require(:post).permit(:title, :slug, : category_id)
  end