Filters.markdown

Filters

Overview

Before filters are run before or after the route has been processed:

before do
  MyStore.connect unless MyStore.connected?
end

get '/' do
  @list = MyStore.load_list
  haml :index
end

Similar to before filters, after filters are run after the request has been processed:

after do
  MyStore.disconnect
end

It is also possible to have multiple filters:

before { do_something }
before { something_else }

get '/' do
  # ...
end

after do
  do_something
end

after do
  something_else
end

Filter context

Filters are run in the same context as routes, and can therefore access all instance variables and helper methods:

helpers do
  attr_reader :current_user
  def user(id) User.find(id) end
end

before { @current_user = user session['user_id'] }

get '/admin' do
  pass unless current_user.admin?
  erb :"admin/index"
end

Changing the response

The return value of a filter is ignored, therefore a request to '/' will return 'yes' for the following Sinatra application:

get('/') { 'yes' }
after { 'no' }

However, it is possible to change the response using halt:

get('/') { return @buisness_secrets }
after { halt 403, 'you almost got me' }

Pattern matching filters

Filters optionally taking a pattern, causing them to be evaluated only if the request path matches that pattern:

before '/protected/*' do
  authenticate!
end

after '/create/:slug' do |slug|
  session[:last_slug] = slug
end