What's the base URL for my app?

问题

In Camping/Rack, how can I get the base URL for my app? I want to know so I can put it in an email it sends.

It might be (in development)

or

http://localhost:9292

or

http://localhost:80/game

or in production

http://fancy-snake.heroku.com

回答1:

Camping has a helper called URL which returns the absolute URL to your app:

URL()               # => #<URL:http://test.ing/blog/>
URL() + "view/12"   # => #<URL:http://test.ing/blog/view/12>
URL("/view/12")     # => #<URL:http://test.ing/blog/view/12>

回答2:

So far I have

url = @env['rack.url_scheme'] + "://" + @env['HTTP_HOST'] + R(LoginX, u.secret)

Which seems to work for the first and third cases. I don't know if it's write if the app is at localhost/prefix

回答3:

You have to be a little careful with this, as there are a some subtle potential traps. The Rack::Request class will probably be helpful here.

First, you can’t really get the url for the app, as it may be responding to multiple urls (via Rack routes, Apache config, etc), so you’re looking at getting the url for the particular request. If you’re only serving requests from one url this won’t matter.

The scheme for the request is in the env hash under the rack.url_scheme, but this is only for the “last leg” of the request. If your app is behind a proxy of some sort (Nqinx, Apache etc.) then you want to get the scheme of the real request, not the request from the proxy to the machine your app is running on. If you’ve configured your proxy correctly it should be setting a header so you can tell what the original scheme was. Rack::Request has a scheme method that takes these headers into account.

The host for the url is probably in the env hash under the HTTP_HOST key, but this header is not necessarily present (admittedly that’s pretty unlikey nowadays). You should fall back on SERVER_NAME and SERVER_PORT. Additionally there’s the issue of handling proxied requests, you want the hostname of the original request, not the backend server. Again, Rack::Request provides host_with_port and host methods that deal with these issues.

Rack::Request also provides a base_url method that combines scheme and host, and additionally only includes the port if differs from the default (80 or 443).

The location that your app is mounted is in the env hash under the SCRIPT_NAME key. This would be /game in your second example, and can be empty if your app mounted at the root of your server. Again, Rack::Request provides a script_name method, although this one simply returns the value of the entry in the env hash.

So, in summary, you probably want to use something like this:

req = Rack::Request.new env
url = req.base_url + req.script_name

which looks pretty simple, but is taking care of various possibilities for you.

Additionally, you miight find the the Rack specification useful to have a read of, it contains details of the various entries that should be in the env hash.

来源：https://stackoverflow.com/questions/12885012/whats-the-base-url-for-my-app