What path is a mountable engine mounted on

Question

I need to know, from inside of a layout of a mountable engine, what path it's currently being mounted on. What would be the way to do it?

E.g. my routes.rb contains the following line:

  mount BackendCore::Engine => "/backend"

From inside of the BackendCore, I need the access to the value of "/backend".

possible duplicate of [Reverse rails routing: find the the action name from the URL](http://stackoverflow.com/questions/3481731/reverse-rails-routing-find-the-the-action-name-from-the-url) — Ben Lee, Sep 28 '11 at 07:23
The link you provide does not help much, as it has no references to engines, although it gives a direction to search in. — mxgrn, Sep 28 '11 at 07:51

Christoph Petschnig · Answer 1 · 2012-02-09T09:40:10.617

10

If the engine is mouted :as => a different name, querying named_routes will not be sufficient. This monkey patch will do:

class Rails::Engine
  def self.mounted_path
    route = Rails.application.routes.routes.detect do |route|
      route.app == self
    end
    route && route.path
  end
end

Now call mounted_path on the engine:

BackendCore::Engine.mounted_path => "/backend"

Note: be careful, in production mode, the classes in your engine are evaluated before the routes of the main app are loaded. Calling this method in class macros might not work!

edited Feb 09 '12 at 09:40

answered Feb 08 '12 at 12:26

Christoph Petschnig

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Using this technique in Rails 4 Engines. Thanks! – RailinginDFW Dec 02 '14 at 22:09

mxgrn · Accepted Answer · 2014-02-11T04:03:17.010

8

UPDATE: this probably applies to Rails 3 only!

I found the solution:

Rails.application.routes.named_routes[:backend_core].path #=> "/backend"

edited Feb 11 '14 at 04:03

answered Sep 28 '11 at 09:09

mxgrn

1,733
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Thanks buddy, this one really helped me out :) – Ryan Bigg Jan 31 '12 at 02:36

score 3 · Answer 3 · answered Mar 10 '16 at 12:54

Evaluating the routes to get the mount path can give unexpected results when engines are mounted inside other engines.

When you take a look at https://github.com/rails/rails/pull/5008 you can read the comment by Jose Valim:

Also, an engine can be mounted inside another engine, so it is unlikely that this will give you the proper result. The best option is probably to have a configuration option where the developer will set the path.

For consistent results, I'm now using an accessor on the engine.

For example:

# APP/initializers/backend_core_engine.rb
BackendCore::Engine.mount_path = "/backend"

# APP/config/routes.rb
mount BackendCore::Engine => BackendCore::Engine.mount_path

# ENGINE/backend_core/lib/engine.rb
module BackendCore
  class Engine < ::Rails::Engine
    cattr_accessor :mount_path
  end
end

score 0 · Answer 4 · answered May 14 '16 at 16:27

0

You could simply use the following code to tell what path engine is mount to inside an engine controller/view:

env["SCRIPT_NAME"] # => "/backend"

answered May 14 '16 at 16:27

Tian Chen

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It shouldn't be possible to get a downvote with no explanation. How can I trust if that downvote makes sense or not? – a.barbieri Nov 30 '17 at 07:33

What path is a mountable engine mounted on

4 Answers4

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