Parse Query Params From A URL

For all of the conveniences that Ruby and Rails affords a developer through their expansive APIs, I am always surprised that it is hard to inspect the query params in a URL.

Let's take a URL and walk through the steps it takes to pull out the value of a query param.

Here's a URL:

url = "https://example.com?taco=bell&taco_count=3"
=> "https://example.com?taco=bell&taco_count=3"

Let's parse the URL with URI:

> URI(url)
=> #<URI::HTTPS https://example.com?taco=bell&taco_count=3>

Then grab the query part of that URI:

> URI(url).query
=> "taco=bell&taco_count=3"

This is an unparsed string. In a Rails context, this can be parsed with Rack::Utils.parse_nested_query:

> query_params = Rack::Utils.parse_nested_query(URI(url).query)
=> {"taco"=>"bell", "taco_count"=>"3"}

And now we have a hash of values we can inspect:

> query_params["taco_count"]
=> "3"

Be sure to do string and not symbol hash access here.

These steps can be wrapped up into a method:

module UrlHelpers
  def query_params(url)
    unparsed_query_params = URI(url).query
    Rack::Utils.parse_nested_query(unparsed_query_params)
  end
end

source