How to extract URL parameters from a URL with Ruby or Rails?

Question

I have some URLs, like

http://www.example.com/something?param1=value1&param2=value2&param3=value3

and I would like to extract the parameters from these URLs and get them in a Hash. Obviously, I could use regular expressions, but I was just wondering if there was easier ways to do that with Ruby or Rails. I haven't found anything in the Ruby module URI but perhaps I missed something.

In fact, I need a method that would do that:

extract_parameters_from_url("http://www.example.com/something?param1=value1&param2=value2&param3=value3")
#=> {:param1 => 'value1', :param2 => 'value2', :param3 => 'value3'}

Would you have some advices?

Solution 1

I think you want to turn any given URL string into a HASH?

You can try http://www.ruby-doc.org/stdlib/libdoc/cgi/rdoc/classes/CGI.html#M000075

require 'cgi'

CGI::parse('param1=value1&param2=value2&param3=value3')

returns

{"param1"=>["value1"], "param2"=>["value2"], "param3"=>["value3"]}

Solution 2

I found myself needing the same thing for a recent project. Building on Levi's solution, here's a cleaner and faster method:

Rack::Utils.parse_nested_query 'param1=value1&param2=value2&param3=value3'
# => {"param1"=>"value1", "param2"=>"value2", "param3"=>"value3"}

Solution 3

Just Improved with Levi answer above -

Rack::Utils.parse_query URI("http://example.com?par=hello&par2=bye").query

For a string like above url, it will return

{ "par" => "hello", "par2" => "bye" } 

Solution 4

For a pure Ruby solution combine URI.parse with CGI.parse (this can be used even if Rails/Rack etc. are not required):

CGI.parse(URI.parse(url).query) 
# =>  {"name1" => ["value1"], "name2" => ["value1", "value2", ...] }

Solution 5

There more than one ways, to solve your problem. Others has shown you the some tricks. I know another trick. Here is my try :-

require 'uri'
url = "http://www.example.com/something?param1=value1&param2=value2&param3=value3"
uri = URI(url)
# => #<URI::HTTP:0x89e4898 URL:http://www.example.com/something?param1=value1&param2=value2&param3=value3>
URI::decode_www_form(uri.query).to_h # if you are in 2.1 or later version of Ruby
# => {"param1"=>"value1", "param2"=>"value2", "param3"=>"value3"}
Hash[URI::decode_www_form(uri.query)] # if you are below 2.1 version of Ruby
# => {"param1"=>"value1", "param2"=>"value2", "param3"=>"value3"}

Read the method docomentation of ::decode_www_form.

View more solutions

Comments

[Vojto]

Hash[*string.split('&').collect{|i|i.split('=')}.flatten] This would work too, but it's probably the worst option for this case. But still you might find this snippet interesting. (Posting as comment since I don't consider this an answer :-))

[Flackou]

OK, I knew that, it works well in the controller with the requested URL, but how to do that for others arbitrary URLs?

[Flackou]

OK, that was the one I missed! It's perfect when used with URI.parse : CGI.parse(URI.parse("example.com/…) returns the desired Hash. Thanks for your help.

[glenn jackman]

For clarity, @Flackou wants this: CGI.parse(URI.parse(url).query)

[Levi]

I haven't tested this, but the first key listed, containing the full url, seems really wrong.

[Gareth]

Much more lightweight than mocking a Rack request

[Levi]

Good find. If you have simple params (non-nested) and are performance sensitive, Rack::Utils.parse_query might be of interest. The code is worth reading: github.com/rack/rack/blob/master/lib/rack/utils.rb

[benathon]

I actually had to use this: CGI::parse(URI::parse(url).query)

[jackocnr]

great answer. simple, processes the full URL like the op asks, and the result values are strings instead of arrays, like in the other answers. thanks.

[Blue Smith]

Thank you, it's very useful :)

[B Seven]

This works well but does not work for checkboxes with the same name: param1=value1&param1=value2. The second value trumps the first.

[zelanix]

For anyone looking for the inverse, it's Rack::Utils.build_nested_query(params) (or Rack::Utils.build_query(params) if parsed with Rack::Utils.parse_query).

[zelanix]

As I commented above, for anyone looking for the inverse, it's Rack::Utils.build_query(params).

[Raels]

Beware - not quite the inverse, at least not in Ruby 1.8.7 / Rails 2.3. A query string of foo[]=1&foo[]=2 is correctly parsed as { "foo" =>["1","2"] }, but build_query turns that into "foo=1&foo=2", which when parsed again yields { "foo"=>"2"}.

[Yossi Shasho]

This method crashes sometimes because of encoding issues. I found the CGI:parse method to be more stable (see answer above)

[wbharding]

Took me a minute to realize that due to lack of wrapping params, this answer isn't readily extended. Rack::Utils.parse_query(URI("http://example.com?par=hello&pa‌​r2=bye").query) yields a hash that can be further modified.

[Kelsey Hannan]

Sadly it looks this gem, like the URI library, has difficulty parsing query parameters in situations where the URL is weird. I.e. both fail to find query parameters when urls are odd, e.g. this: http://localhost:4300/webapp/foo/#//controller/action? Leaving me to use a hack like: Rack::Utils.parse_nested_query(url.split("?").last) to get the query parameters for parsing.

[Michael Brawn]

Look, no additional libraries needed 👍

[Jason L.]

This is elegant.