Render HTML file in Rails using Nokogiri

You may need to render static HTML template file from a controller action without modifying anything in to file. And, may need to replace some content during render.

A template may contain relative path for css, image etc. which may raise an exception as rails may not route that automatically. At that case you have to change the contents but that’s not straightforward.

I have given an example below to render a static newsletter template placed in to public directory

Say, you have a newsletter template in to public/newsletters/1.html which contains something like below and want to render from newsletters#show:





{title}

{description}

Write a library to process newsletter template and placed in to lib

require 'nokogiri'
require 'uri'

module NewsletterProcessor
TEMPLATE_DIR = "newsletter-template"
TEMPLATE_PATH = "public/#{TEMPLATE_DIR}/1.html"

def self.included(base)
base.send(:before_filter, :load_newsletter, :only => :show)
end

def show
content = render_to_string(:file => TEMPLATE_PATH)
@content = TemplateParser.new(request, @newsletter.attributes).parse(content)
render :text => @content, :layout => false
end

private

def load_newsletter
@newsletter = Newsletter.find(params[:id])
end

class TemplateParser
cattr_accessor :request
cattr_accessor :params

def initialize(request, attrs)
self.request = request
self.params = attrs
end

def parse(content)
content = Nokogiri::HTML(content)
return parse_content(parse_assets_url(content))
end

private

def parse_assets_url(content)
#Parse Image URL
content.css("img").each do |img|
update_asset_attribute(img, "src")
end

#Parse Stylesheet URL
content.css("link").each do |link|
update_asset_attribute(link, "href")
end

return content
end

def parse_content(content)
content = content.to_s
content.gsub!(/{(.*)}/) do |exp|
replace_attribute_value(exp)
end

return content
end

def replace_attribute_value(exp, attributes = self.params)
key = exp.delete('{}').downcase.to_sym
attributes.has_key?(key) ? attributes[key] : exp
end

def update_asset_attribute(ele, key)
path = ele.attributes[key].value
ele.attributes[key].value = full_url(path)
end

def full_url(path)
url = URI.parse(path)
return !url.scheme ? "#{self.request.scheme}://#{self.request.host_with_port}/#{TEMPLATE_DIR}/#{url.path}" : path
end
end
end

Now, just include the library in to the newsletters controller and run newsletters#show from browser.

class NewslettersController < ApplicationController
include NewsletterProcessor
end

That’s all!

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