gistfile1.rb

class PostsController < ActionController::Base
  def create
    Post.create(post_params)
  end
  
  def update
    Post.find(params[:id]).update_attributes!(post_params)
  end

  private
    def post_params
      params[:post].slice(Post.web_accessible)
    end
end

post.rb

class Post
  def self.web_accessible
    [:title, :body]
  end

  def self.api_accessible
    [:title]
  end
end