simple templating

photo_essay.rb

#!/usr/bin/ruby

require 'yaml'

# DATA is a little-used feature of the Ruby language; it's a file handle
# whose contents are everything in the current file after the __END__.
# YAML is "Yet Another Markup Language".
data = YAML.load(DATA)

def url_for(entry_num)
  "/photo_essay/#{entry_num}.html"
end

data[:entries].each_with_index do |entry, index| 
  index += 1 # start from entry 1 instead of 0

  # treat any word in the template surrounded by double curly brackets
  # as a substitution variable. there are more full-fledged templating
  # libraries, e.g. Liquid, but I wanted to keep this simple.
  output = data[:template].gsub(/\{\{(\w+)\}\}/) do |match|
    # $1 is the first matching group; you would also have $2, $3, etc. 
    # if the regex had more matching groups.
    case $1
    when "next_url"
      url_for(index == data[:entries].size ? 1 : index + 1)
    else
      entry[$1]
    end
  end
  
  puts "entry #{index}"
  puts output
  # to save files:
  # open("#{index + 1}.html", "w") {|file| file.write(output) }
end

__END__
:entries:
  -
    photo: foo.jpg
    blurb: this is a very short blurb
  -
    photo: bar.jpg
    blurb: 
      Lorem ipsum dolor sit amet, consectetur adipisicing elit, 
      sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. 
      Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris 
      nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in 
      reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla 
      pariatur. Excepteur sint occaecat cupidatat non proident, sunt in 
      culpa qui officia deserunt mollit anim id est laborum.
  -
    photo: baz.jpg
    blurb: hmm hmm hmm

:template:
  <div class="entry">
    <img src="{{photo}}"/>
    <div class="blurb">
      {{blurb}}
    </div>
    <a href="{{next_url}}">next entry</a>
  </div>