#Rails - Insert attributes into Request Params

posts-controller.rb

class PostsController < ApplicationController
  
  def create
    Post.create!(post_params)
  end
  
  private
  
  def post_params
    params.require(post).permit(:some_attrs).merge(user_id: current_user.id)
  end
  
end

See: http://stackoverflow.com/questions/16530532/rails-4-insert-attribute-into-params