# class Rack::Cascade

`Rack::Cascade` tries a request on several apps, and returns the first response that is not 404 or 405 (or in a list of configured status codes). If all applications tried return one of the configured status codes, return the last response.

### Constants

NotFound

  deprecated, no longer used

### Attributes

apps[R]

An array of applications to try in order.

### Public Class Methods

new(apps, cascade_for = [404, 405]) click to toggle source

Set the apps to send requests to, and what statuses result in cascading. Arguments:

apps: An enumerable of rack applications. cascade_for: The statuses to use cascading for. If a response is received

    from an app, the next app is tried.

    # File lib/rack/cascade.rb, line 22
    def initialize(apps, cascade_for = [404, 405])
      @apps = []
      apps.each { |app| add app }

      @cascade_for = {}
      [*cascade_for].each { |status| @cascade_for[status] = true }
    end

### Public Instance Methods

<<(app)
Alias for: add
add(app) click to toggle source

Append an app to the list of apps to cascade. This app will be tried last.

    # File lib/rack/cascade.rb, line 57
    def add(app)
      @apps << app
    end

Also aliased as: <<
call(env) click to toggle source

Call each app in order. If the responses uses a status that requires cascading, try the next app. If all responses require cascading, return the response from the last app.

    # File lib/rack/cascade.rb, line 33
    def call(env)
      return [404, { CONTENT_TYPE => "text/plain" }, []] if @apps.empty?
      result = nil
      last_body = nil

      @apps.each do |app|
        # The SPEC says that the body must be closed after it has been iterated
        # by the server, or if it is replaced by a middleware action. Cascade
        # replaces the body each time a cascade happens. It is assumed that nil
        # does not respond to close, otherwise the previous application body
        # will be closed. The final application body will not be closed, as it
        # will be passed to the server as a result.
        last_body.close if last_body.respond_to? :close

        result = app.call(env)
        return result unless @cascade_for.include?(result[0].to_i)
        last_body = result[2]
      end

      result
    end

include?(app) click to toggle source

Whether the given app is one of the apps to cascade to.

    # File lib/rack/cascade.rb, line 62
    def include?(app)
      @apps.include?(app)
    end