I would like to be able to map URLs to Controllers dynamically based on information in my database.

I'm looking to do something functionally equivalent to this (assuming a View model):

map.route '/:view_name',
    :controller => lambda { View.find_by_name(params[:开发者_运维技巧view_name]).controller }

Others have suggested dynamically rebuilding the routes, but this won't work for me as there may be thousands of Views that map to the same Controller

This question is old, but I found it interesting. A fully working solution can be created in Rails 3 using router's capability to route to a Rack endpoint.

Create the following Rack class:

    class MyRouter
      def call(env)
        # Matched from routes, you can access all matched parameters
        view_name= env['action_dispatch.request.path_parameters'][:view_name]

        # Compute these the way you like, possibly using view_name
        controller= 'post' 
        my_action= 'show'

        controller_class= (controller + '_controller').camelize.constantize
        controller_class.action(my_action.to_sym).call(env)
      end
    end

In Routes

    match '/:view_name', :to => MyRouter.new, :via => :get

Hint picked up from http://guides.rubyonrails.org/routing.html#routing-to-rack-applications which says "For the curious, 'posts#index' actually expands out to PostsController.action(:index), which returns a valid Rack application."

A variant tested in Rails 3.2.13.

So I think that you are asking that if you have a Views table and a View model for it where the table looks like

id | name | model
===================
1  | aaa  | Post
2  | bbb  | Post
3  | ccc  | Comment

You want a url of /aaa to point to Post.controller - is this right?

If not then what you suggest seems fine assuming it works.

You could send it to a catch all action and have the action look at the url, run the find_by_name and then call the correct controller from there.

def catch_all
  View.find_by_name('aaa').controller.action
end

Update

You can use redirect_to and even send the params. In the example below you I am sending the search parameters

def catch_all
  new_controller = View.find_by_name('aaa').controller
  redirect_to :controller => new_controller, :action => :index, 
      :search => params[:search] 
end

Here is a nice Rack Routing solution to SEO contributed by zetetic and Steve ross

Testing Rack Routing Using rSpec

It shows you how to write a custom dispatcher (where you can do a db lookup if needed) and with constraints, and testing as well.

As suggested in the question Rails routing to handle multiple domains on single application, I guess you could use Rails Routing - Advanced Constraints to build what you need.

If you have a limited space of controllers (with unlimited views pointing to them), this should work. Just create a constraint for each controller that verifies if the current view matches them.

Assuming you have a space of 2 controllers (PostController and CommentController), you could add the following to your routes.rb:

match "*path" => "post#show", :constraints => PostConstraint.new
match "*path" => "comment#show", :constraints => CommentConstraint.new

Then, create lib/post_constraint.rb:

class PostConstraint     
  def matches?(request)
    'post' == Rails.cache.fetch("/view_controller_map/#{request.params[:view_name]}") { View.find_by_name(request.params[:view_name]).controller }
  end
end

Finally, create lib/comment_constraint.rb:

class CommentConstraint     
  def matches?(request)
    'comment' == Rails.cache.fetch("/view_controller_map/#{request.params[:view_name]}") { View.find_by_name(request.params[:view_name]).controller }
  end
end

You can do some improvements, like defining a super constraint class that fetches the cache, so you don't have to repeat code and don't risk fetching a wrong cache key name in one of the constraints.