Question

For instance, I want to find the constructor of ActionController::RoutingError at http://api.rubyonrails.org/. I typed ActionController::RoutingError or RoutingError in the search box, nothing got returned.

Answer 1

This is a bad example. See the source:

  class RoutingError < ActionControllerError #:nodoc:
    attr_reader :failures
    def initialize(message, failures=[])
      super(message)
      @failures = failures
    end
  end

There’s no documentation for the class.

Also try http://apidock.com/rails — this resource can be more helpful in general.