實現 Markdown 語法和代碼語法高亮分別是用的 Redcarpet 和 pygments.rb 兩個 Gem：
https://github.com/vmg/redcarpet
https://github.com/tmm1/pygments.rb
https://github.com/richleland/pygments-css
http://pygments.org/docs/lexers/
在/Gemfile中添加如下兩行：
gem 'redcarpet'gem 'pygments.rb'
需要說明的是，pygments.rb 依賴于 Python，所以確保機器已經安裝了 Python 2.x。
然后在/app/controllers/comments_controller.rb中添加相應 redcarpet 和 pygments.rb 的代碼：
class ApplicationController < ActionController::Base # Prevent CSRF attacks by raising an exception. # For APIs, you may want to use :null_session instead. protect_from_forgery with: :exception helper_method [:markdown] # Highlight code with Pygments class HTMLwithPygments < Redcarpet::Render::HTML def block_code(code, language) language = "text" if language.blank? sha = Digest::SHA1.hexdigest(code) Rails.cache.fetch ["code", language, sha].join("-") do Pygments.highlight(code, :lexer => language) end end end protected # Markdown with Redcarpet def markdown(text) renderer = HTMLwithPygments.new({ :filter_html => true, :hard_wrap => true, :link_attributes => {:rel => 'external nofollow'} }) options = { :autolink => true, :no_intra_emphasis => true, :fenced_code_blocks => true, :lax_html_blocks => true, :strikethrough => true, :superscript => true, :tables => true } Redcarpet::Markdown.new(renderer, options).render(text).html_safe endend最后在 View 中就可以直接調用 markdown 方法來處理博客正文了：
<%= markdown @post.content %>
語法規則類似 Github 上的 Markdown，碼字效率大大提高。
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