app/controllers/thredded/post_previews_controller.rb
def preview
      @post = Thredded::Post.new(post_params)
      @post.postable = Thredded::Topic.friendly_find!(params[:topic_id])
      authorize @post, :create?
      render_preview
    end
def preview
      @post = Thredded::Post.new(post_params)
      @post.postable = Thredded::Topic.friendly_find!(params[:topic_id])
      authorize @post, :create?
      render_preview
    end
Preview a new post