Problem

In Rails, I needed to take the request url and redirect the user to a new host with additional query parameters while passing the original path and query parameters.

For example, if the original request looked like:

"http://www.mystore.com/cart?sort=desc"

I needed to redirect them to:

"https://mobile.mystore.com/cart?sort=desc&view=ipad"

While this could be done with fancy string manipulation, I figured there had to be a cleaner and less error prone way.

Solution

There is a great utility in Ruby Core to handle URL manipulation. Unfortunately, it isn’t well documented.

There is a kernal level method named URI which parses the full url and breaks it down into parts

# request.url = http://www.mystore.com/cart?sort=desc
uri = URI(request.url)
puts uri.host # www.mystore.com
puts uri.scheme # http
puts uri.query # sort=desc

To swap the host and scheme was easy enough

uri.host = "mobile.mystore.com"
uri.scheme = "https"

To modify the query parameters, we had to consider the possiblity of no parameters. In that case, the uri.query would be nil. The query parameters are only broken down into a string, so we have to split, add and join them back together.

query = uri.query ? uri.query.split('&') : []
query << "view=ipad"
uri.query = query.join('&')

Then we just have to reconstruct the url and redirect the user

redirect_to uri.to_s # https://mobile.mystore.com/cart?sort=desc&view=ipad

Conclusion

There is always a cleaner way.