Sinatra::RespondWith

These extensions let Sinatra automatically choose what template to render or action to perform depending on the request‘s Accept header.

Example:

  # Without Sinatra::RespondWith
  get '/' do
    data = { :name => 'example' }
    request.accept.each do |type|
      case type.to_s
      when 'text/html'
        halt haml(:index, :locals => data)
      when 'text/json'
        halt data.to_json
      when 'application/atom+xml'
        halt nokogiri(:'index.atom', :locals => data)
      when 'application/xml', 'text/xml'
        halt nokogiri(:'index.xml', :locals => data)
      when 'text/plain'
        halt 'just an example'
      end
    end
    error 406
  end

  # With Sinatra::RespondWith
  get '/' do
    respond_with :index, :name => 'example' do |f|
      f.txt { 'just an example' }
    end
  end

Both helper methods respond_to and respond_with let you define custom handlers like the one above for +text/plain+. respond_with additionally takes a template name and/or an object to offer the following default behavior:

• If a template name is given, search for a template called +name.format.engine+ (+index.xml.nokogiri+ in the above example).
• If a template name is given, search for a templated called +name.engine+ for engines known to result in the requested format (+index.haml+).
• If a file extension associated with the mime type is known to Sinatra, and the object responds to to_extension, call that method and use the result (+data.to_json+).

Security

Since methods are triggered based on client input, this can lead to security issues (but not as severe as those might appear in the first place: keep in mind that only known file extensions are used). You should limit the possible formats you serve.

This is possible with the provides condition:

  get '/', :provides => [:html, :json, :xml, :atom] do
    respond_with :index, :name => 'example'
  end

However, since you have to set provides for every route, this extension adds an app global (class method) `respond_to`, that lets you define content types for all routes:

  respond_to :html, :json, :xml, :atom
  get('/a') { respond_with :index, :name => 'a' }
  get('/b') { respond_with :index, :name => 'b' }

Custom Types

Use the on method for defining actions for custom types:

  get '/' do
    respond_to do |f|
      f.xml { nokogiri :index }
      f.on('application/custom') { custom_action }
      f.on('text/*') { data.to_s }
      f.on('*/*') { "matches everything" }
    end
  end

Definition order does not matter.