constraints

Parameter Restriction

Allows you to constrain the nested routes based on a set of rules. For instance, in order to change the routes to allow for a dot character in the id parameter:

constraints(id: /\d+\.\d+/) do
  resources :posts
end

Now routes such as /posts/1 will no longer be valid, but /posts/1.1 will be. The id parameter must match the constraint passed in for this example.

You may use this to also restrict other parameters:

resources :posts do
  constraints(post_id: /\d+\.\d+/) do
    resources :comments
  end
end

Restricting based on IP

Routes can also be constrained to an IP or a certain range of IP addresses:

constraints(ip: /192\.168\.\d+\.\d+/) do
  resources :posts
end

Any user connecting from the 192.168.* range will be able to see this resource, where as any user connecting outside of this range will be told there is no such route.

Dynamic request matching

Requests to routes can be constrained based on specific criteria:

constraints(-> (req) { req.env["HTTP_USER_AGENT"] =~ /iPhone/ }) do
  resources :iphones
end

You are able to move this logic out into a class if it is too complex for routes. This class must have a matches? method defined on it which either returns true if the user should be given access to that route, or false if the user should not.

class Iphone
  def self.matches?(request)
    request.env["HTTP_USER_AGENT"] =~ /iPhone/
  end
end

An expected place for this code would be lib/constraints.

This class is then used like this:

constraints(Iphone) do
  resources :iphones
end