Do you think the Ruby on Rails web framework is a massive monster - more than 10,000+ lines of code
just for ActionPack - not counting ActiveModel, ActiveRecord, ActiveJob, ActiveResource
and what not?
Or do you think that even the "classic" Sinatra web machinery clocking
in at more than 1,000+ lines of code
is more macro than micro?
Why not write a "real" micro web framework inspired by Konstantin Haase's Almost Sinatra hack that ships as a 6(!) lines of code pastie:
almost_sinatra.rb:
%w.rack tilt date INT TERM..map{|l|trap(l){$r.stop}rescue require l};$u=Date;$z=($u.new.year + 145).abs;puts "== Almost Sinatra/No Version has taken the stage on #$z for development with backup from Webrick"
$n=Module.new{extend Rack;a,D,S,q=Rack::Builder.new,Object.method(:define_method),/@@ *([^\n]+)\n(((?!@@)[^\n]*\n)*)/m
%w[get post put delete].map{|m|D.(m){|u,&b|a.map(u){run->(e){[200,{"Content-Type"=>"text/html"},[a.instance_eval(&b)]]}}}}
Tilt.mappings.map{|k,v|D.(k){|n,*o|$t||=(h=$u._jisx0301("hash, please");File.read(caller[0][/^[^:]+/]).scan(S){|a,b|h[a]=b};h);v[0].new(*o){n=="#{n}"?n:$t[n.to_s]}.render(a,o[0].try(:[],:locals)||{})}}
%w[set enable disable configure helpers use register].map{|m|D.(m){|*_,&b|b.try :[]}};END{Rack::Handler.get("webrick").run(a,Port:$z){|s|$r=s}}
%w[params session].map{|m|D.(m){q.send m}};a.use Rack::Session::Cookie;a.use Rack::Lock;D.(:before){|&b|a.use Rack::Config,&b};before{|e|q=Rack::Request.new e;q.params.dup.map{|k,v|params[k.to_sym]=v}}}
Of course - the "magic" is possible because all the machinery and heavy-lifting
gets outsourced to rack and to the lesser known tilt library.
Let's thank Ryan Tomayko, Magnus Holm and friends for creating the tilt gem offering a standard "generic" interface for template engines that you can use - surprise, surprise - for building your own web frameworks or static site generators, for example.
Let's check-up what formats and template engines tilt includes out-of-the-box:
require 'tilt'
Tilt.mappings.each do |ext, engines|
puts "#{ext.ljust(12)} : #{engines.inspect}"
end
Will result in:
str : [Tilt::StringTemplate]
erb : [Tilt::ErubisTemplate, Tilt::ERBTemplate]
rhtml : [Tilt::ErubisTemplate, Tilt::ERBTemplate]
erubis : [Tilt::ErubisTemplate]
etn : [Tilt::EtanniTemplate]
etanni : [Tilt::EtanniTemplate]
haml : [Tilt::HamlTemplate]
sass : [Tilt::SassTemplate]
scss : [Tilt::ScssTemplate]
less : [Tilt::LessTemplate]
rcsv : [Tilt::CSVTemplate]
coffee : [Tilt::CoffeeScriptTemplate]
nokogiri : [Tilt::NokogiriTemplate]
builder : [Tilt::BuilderTemplate]
mab : [Tilt::MarkabyTemplate]
liquid : [Tilt::LiquidTemplate]
radius : [Tilt::RadiusTemplate]
markdown : [Tilt::RedcarpetTemplate, Tilt::RedcarpetTemplate::Redcarpet2, Tilt::RedcarpetTemplate::Redcarpet1, Tilt::RDiscountTemplate, Tilt::BlueClothTemplate, Tilt::KramdownTemplate, Tilt::MarukuTemplate]
mkd : [Tilt::RedcarpetTemplate, Tilt::RedcarpetTemplate::Redcarpet2, Tilt::RedcarpetTemplate::Redcarpet1, Tilt::RDiscountTemplate, Tilt::BlueClothTemplate, Tilt::KramdownTemplate, Tilt::MarukuTemplate]
md : [Tilt::RedcarpetTemplate, Tilt::RedcarpetTemplate::Redcarpet2, Tilt::RedcarpetTemplate::Redcarpet1, Tilt::RDiscountTemplate, Tilt::BlueClothTemplate, Tilt::KramdownTemplate, Tilt::MarukuTemplate]
textile : [Tilt::RedClothTemplate]
rdoc : [Tilt::RDocTemplate]
wiki : [Tilt::WikiClothTemplate, Tilt::CreoleTemplate]
creole : [Tilt::CreoleTemplate]
mediawiki : [Tilt::WikiClothTemplate]
mw : [Tilt::WikiClothTemplate]
yajl : [Tilt::YajlTemplate]
ad : [Tilt::AsciidoctorTemplate]
adoc : [Tilt::AsciidoctorTemplate]
asciidoc : [Tilt::AsciidoctorTemplate]
html : [Tilt::PlainTemplate]
Wow. That's quite an offering. Let's see tilt in action and let's unroll the six somewhat obfuscated lines of Almost Sinatra to see its full inner beauty.
almost_sinatra_ii.rb:
# Note: to keep it simple; the inline template machinery e.g. S=/@@ *([^\n]+)\n(((?!@@)[^\n]*\n)*)/m
and the before, configure 'n' friends blocks got dropped
## line 1
# %w.rack tilt date INT TERM..map{|l|trap(l){$r.stop}rescue require l};$u=Date;$z=($u.new.year + 145).abs;puts "== Almost Sinatra/No Version has taken the stage on #$z for development with backup from Webrick"
require 'rack'
require 'tilt'
trap( 'INT' ) { $server.stop } # rename $r to $server
trap( 'TERM' ) { $server.stop }
$port = 4567 # rename $z to $port
puts "== Almost Sinatra II has taken the stage on #{$port} for development with backup from Webrick"
## line 2
# $n=Module.new{extend Rack;a,D,S,q=Rack::Builder.new,Object.method(:define_method),/@@ *([^\n]+)\n(((?!@@)[^\n]*\n)*)/m
$n = Module.new do
app = Rack::Builder.new # rename a to app
req = nil # rename q to req
## line 3
# %w[get post put delete].map{|m|D.(m){|u,&b|a.map(u){run->(e){[200,{"Content-Type"=>"text/html"},[a.instance_eval(&b)]]}}}}
['get','post','put','delete'].each do |method|
define_method method do |path, &block|
app.map( path ) do
run ->(env){ [200, {'Content-Type'=>'text/html'}, [app.instance_eval( &block )]]}
end
end
end
## line 4
# Tilt.mappings.map{|k,v|D.(k){|n,*o|$t||=(h=$u._jisx0301("hash, please");File.read(caller[0][/^[^:]+/]).scan(S){|a,b|h[a]=b};h);v[0].new(*o){n=="#{n}"?n:$t[n.to_s]}.render(a,o[0].try(:[],:locals)||{})}}
Tilt.mappings.each do |ext, engines| # rename k to ext and v to engines
define_method ext do |text, *args| # rename n to text and o to args
template = engines[0].new(*args) do
text
end
locals = (args[0].respond_to?(:[]) ? args[0][:locals] : nil) || {} # was o[0].try(:[],:locals)||{}
template.render( app, locals )
end
end
## line 5
# %w[set enable disable configure helpers use register].map{|m|D.(m){|*_,&b|b.try :[]}};END{Rack::Handler.get("webrick").run(a,Port:$z){|s|$r=s}}
# was END { ... }; change to run! method
define_method 'run!' do
Rack::Handler.get('webrick').run( app, Port:$port ) {|server| $server=server }
end
## line 6
# %w[params session].map{|m|D.(m){q.send m}};a.use Rack::Session::Cookie;a.use Rack::Lock;D.(:before){|&b|a.use Rack::Config,&b};before{|e|q=Rack::Request.new e;q.params.dup.map{|k,v|params[k.to_sym]=v}}}
['params','session'].each do |method|
define_method method do
req.send method
end
end
app.use Rack::Session::Cookie
app.use Rack::Lock
app.use Rack::Config do |env|
req = Rack::Request.new( env )
end
end # Module.new
All the tilt magic happens in line 4. Almost Sinatra will define a method for every format so you can use, for example:
markdown 'Strong emphasis, aka bold, with **asterisks** or __underscores__.'
or
erb "Hello <%= name %>!", locals: { name: params['name'] }
Let's try the embedded ruby (erb) example by hand:
require 'tilt'
template = Tilt::ErubisTemplate.new do # Step 1: create a template
"Hello <%= name %>!"
end
puts template.render( self, name: 'World' ) # Step 2: render the template
# There's no step 3 ;-)
Or to more closely reflect the Almost Sinatra setup:
require 'tilt'
text = "Hello <%= name %>!"
params = { name: 'World' }
args = [ { locals: { name: params[:name] } } ]
template = Tilt::ErubisTemplate.new do
text
end
locals = args[0][:locals]
puts template.render( self, locals )
Resulting in:
Hello World!
The proof of the pudding. To wrap up let's fire up Almost Sinatra II with an example app that renders a document (template) in markdown and another with embedded ruby (erb).
example.rb:
require_relative 'almost_sinatra_ii'
include $n # include "anonymous" Almost Sinatra DSL module
get '/' do
markdown <<EOS
## Welcome to Tilt
A Generic interface to multiple template engines
Try:
- [Say hello!](/hello?name=Tilt)
Powered by Almost Sinatra II (#{Time.now})
EOS
end
get '/hello' do
erb "Hello <%= name %>!", locals: { name: params['name'] }
end
run!
Use
$ ruby ./example.rb
to startup the example app. Resulting in:
== Almost Sinatra II has taken the stage on 4567 for development with backup from Webrick
[2015-04-18 14:42:21] INFO WEBrick 1.3.1
[2015-04-18 14:42:21] INFO ruby 2.1.4 (2014-10-27) [i686-linux]
[2015-04-18 14:42:21] INFO WEBrick::HTTPServer#start: pid=3955 port=4567
Open up your browser @ http://localhost:4567 or http://localhost:4567/hello?name=Tilt.
Voila.
Almost Sinatra
- home :: github.com/rkh/almost-sinatra
- article :: Decoding "Almost Sinatra", by Rob Miller
- article :: Code Safari: Almost Sinatra, Almost Readable, by Xavier Shay
Tilt
- home :: github.com/rtomayko/tilt
- gem :: rubygems.org/gems/tilt
- rdoc :: rubydoc.info/gems/tilt