What's New in Sinatra 1.2?

By Konstantin Haase on Thursday, March 3, 2011

As announced on the mailing list, we have just released Sinatra 1.2.0. Let’s have a closer look at the new features.

Slim support

Sinatra now supports the Slim Template Engine:

require 'sinatra'
require 'slim'

get('/') { slim :index }

__END__

@@ index
! doctype html
html
  head
    title Sinatra With Slim
  body
    h1 Slim Is Fun!
    a href="http://haml-lang.com/" A bit like Haml, don't you think?

Inline Markaby

Like Builder and Nokogiri templates, Markaby can now be used directly inline:

require 'sinatra'
require 'markaby'

get '/' do
  markaby do
    html do
      head { title "Sinatra With Markaby" }
      body { h1 "Markaby Is Fun!" }
    end
  end
end

Layout Engines

Whenever you render a template, like some_page.haml, Sinatra will use a corresponding layout, like layout.haml for you. With the :layout option it has always been possible to use a different layout, but it still had to be written in the same template language, Haml in our example. In 1.1 we introduced markdown, textile and rdoc templates. It is not possible to use those for layouts. We therefore added the :layout_engine option, which easily allows you to combine one two different template engines:

require 'sinatra'
require 'rdiscount'

# for all markdown files, use post.haml as layout
set :markdown, :layout_engine => :haml, :layout => :post

get '/' do
  # use index.haml for readme
  markdown :README, :layout => :index
end

get '/:post' do
  markdown params[:post].to_sym
end

This feature should also be handy when migrating from one template language to another, as it allows you to combine Erb with Haml, for instance.

Conditional Filters

We introduced pattern matching filters in 1.1. Now they also support conditions:

before :agent => /Song Bird/ do
  # ...
end

Those can also be combined with patterns, of course:

after '/api/*', :provides => :json do
  # ...
end

URL helper

Usually Sinatra does not provide any view helper methods. Those are provided by extensions and would not suit Sinatra’s approach of a small but robust core. However, constructing URLs is a use case most people run into sooner or later. It is a bit complicated to construct URLs right. Consider this example:

get('/foo') { "<a href='/bar'>Will you make it?</a>" }
get('/bar') { "You made it!" }

Feel free to run it. Works, doesn’t it? So, what is wrong with it?

Imagine your app is “mounted” by another Rack application, for instance in a config.ru like this:

map('/there') { run Sinatra::Application }
map('/') { run MyRailsApp::Application }

Now the link to /bar would end up in a request send to MyRailsApp rather than to Sinatra. Injecting request.script_name would fix this, but be honest, how often do you do that?

Now, imagine these links are presented out of context, in an RSS feed or embedded on another host. In that case you might want to construct absolute URLs. This is even more cumbersome, as you most certainly either forget to handle reverse proxies, alternative ports/protocols or you end up with lots of URL related code all over the place, while what you should do is use the url helper:

get('/foo') { "<a href='#{url '/bar'}'>You will make it!</a>" }
get('/bar') { "You made it!" }

Since you are likely going to use this with redirects, we also aliased the helper to to:

get('/foo') { redirect to('/bar') }
get('/bar') { "You made it!" }

Named Captures on 1.9

Ruby 1.9 introduced named captures for regular expressions. Sinatra accepts regular expressions for matching paths. Now named captures will automatically end up populating params:

get %r{/(?<year>\d{4})/(?<month>\d{2})/(?<day>\d{2})/?} do
  date = Date.new params[:year].to_i, params[:month].to_i, params[:day].to_i
  @posts = Post.pubished_on date
  erb :posts
end

Templates with different scopes

All rendering methods now accept a :scope options:

get '/:id' do |id|
  @post = Post.find id

  # without scope
  erb "<%= @post.name %>"

  # with scope
  erb "<%= name %>", :scope => @post
end

Note that all Sinatra helper methods and instance variables will not be available.

Configurable redirects

In 1.1 we made sure all redirects were absolute URIs, to conform with RFC 2616 (HTTP 1.1). This will result in issues for you if you have a broken Reverse Proxy configuration. If so, you should really fix your configuration. If you are unable to do so, a simple disable :absolute_redirects will now give you back the 1.0 behavior. As shown above, you can now use the to helper with redirect. If all your redirects are application local, you can now enable :prefixed_redirects and skip the to altogether:

enable :prefixed_redirects
get('/foo') { redirect '/bar' }
get('/bar') { "You made it!" }

We did not enable this per default to not break compatibility and to allow you redirects to other Rack endpoints.

Overriding template lookup

One popular feature request is supporting multiple view folders. But everyone wants different semantics. So, instead of choosing one way to go, we gave you means to implement your own lookup logic:

helpers do
  def find_template(*)
    puts "looking for index.txt"
    yield "views/index.txt"
    puts "apparently, index.txt doesn't exist, let's try index.html"
    yield "views/index.html"
  end
end

get "/" do
  haml :foo
end

Sinatra will call find_template to discover the template file. In the above example, we don’t care about what template engine to use or what name the template has. It will use views/index.txt or views/index.html for every template. Let’s have a look at the standard implementation:

def find_template(views, name, engine)
  Tilt.mappings.each do |ext, klass|
    next unless klass == engine
    yield ::File.join(views, "#{name}.#{ext}")
  end
end

As you can see, it will look in the views folder for a file named like the template with any of the file extensions registered for the template engine.

If all you want to change is the folder, you probably should just call super:

def find_template(views, *a, &b)
  super("#{views}/a", *a, &b)
  super("#{views}/b", *a, &b)
end

More examples can be found in the readme.

Other changes

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