faq.markdown

title	layout
Sinatra: Frequently Asked Questions	default

Frequently Asked Questions

How do I use sessions?

Sessions are disabled by default. You need to enable them and then use the session hash from routes and views:

enable :sessions

get '/foo' do
  session[:message] = 'Hello World!'
  redirect '/bar'
end

get '/bar' do
  session[:message]   # => 'Hello World!'
end

Can I run Sinatra under Ruby 1.9?

Not yet. Rack is not yet Ruby 1.9 compatible and Sinatra is very much dependent on Rack. We are in the early stages of testing under 1.9 and we're reviewing all new code and idioms for potential 1.9 compatibility issues. The 1.0 release (currently scheduled for mid 2009) will run on 1.9 and chances are good that we'll support 1.9 before then.

How do I get the "route" for the current page?

The request object probably has what you're looking for:

get '/hello-world' do
  request.path_info   # => '/hello-world'
  request.fullpath    # => '/hello-world?foo=bar'
  request.url         # => 'http://example.com/hello-world?foo=bar'
end

See Rack::Request for a detailed list of methods supported by the request object.

How do I access helpers from within my views?

Call them! Views automatically have access to all helper methods. In fact, Sinatra evaluates routes, views, and helpers within the same exact object context so they all have access to the same methods and instance variables.

In hello.rb:

helpers do
  def em(text)
    "<em>#{text}</em>"
  end
end

get '/hello' do
  @subject = 'World'
  haml :hello
end

In views/hello.haml:

%p= "Hello " + em(@subject)

How do I render partials?

Sinatra's template system is simple enough that it can be used for page and fragment level rendering tasks. The erb and haml methods simply return a string. However, you need to make sure you disable layout rendering as follows:

<%= erb(:mypartial, :layout => false) %>

See Chris Schneider's partials.rb for a more robust partials implementation. It even supports rendering collections.

Can I have multiple URLs trigger the same route/handler?

Sure:

["/foo", "/bar", "/baz"].each do |path|
  get path do
    "You've reached me at #{request.path_info}"
  end
end

Seriously.

How do I make the trailing slash optional?

Put a question mark after it:

get '/foo/bar/?' do
  "Hello World"
end

The route matches "/foo/bar" and "/foo/bar/".

How do I render templates nested in subdirectories?

Sinatra apps do not typically have a very complex file heirarchy under views. First, consider whether you really need subdirectories at all. If so, you can use the views/foo/bar.haml file as a template with:

get '/' do
  haml :'foo/bar'
end

This is basically the same as sending #to_sym to the filename and can also be written as:

get '/' do
  haml 'foo/bar'.to_sym
end

I'm running Thin and an error occurs but there's no output

Try starting Thin with the --debug argument:

thin --debug --rackup config.ru start

That should give you an exception and backtrace on stderr.

How do I send Email from Sinatra?

How about a Pony (sudo gem install pony):

require 'pony'
post '/signup' do
  Pony.mail :to => '[email protected]',
    :from => '[email protected]',
    :subject => 'Howdy, Partna!'
end

You can even use templates to render the body. In email.erb:

Good day <%= params[:name] %>,

Thanks for my signing my guestbook. You're a doll.

Frank

And in mailerapp.rb:

post '/guestbook/sign' do
  Pony.mail :to => params[:email],
    :from => "[email protected]",
    :subject => "Thanks for signing my guestbook, #{params[:name]}!",
    :body => erb(:email)
end

What are my deployment options?

See the book.

How do I escape html?

Include Rack::Utils in your helpers and create an h alias as follows:

helpers do
  include Rack::Utils
  alias_method :h, :escape_html
end

Now you can escape html in your templates like this:

<%= h scary_output %>

Thanks to Chris Schneider for the tip!