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?

Rosado

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 :-)) – Phenolic

Answer 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"]}

Substantialize

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. – Rosado

For clarity, @Rosado wants this: CGI.parse(URI.parse(url).query) – Cotinga

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

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

This solution won't work properly with arrays, like a[]=1&a[]=2 will be parsed as {"a[]"=>["1", "2"]} whereas Arthur's solution will parse {"a"=>["1", "2"]} – Egocentrism

Answer 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"}

Qualifier

Much more lightweight than mocking a Rack request – Onto

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 – Goren

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

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). – Robalo

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

Answer 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" } 

Seiter

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. – Burp

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

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"}. – Nee

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&par2=bye").query) yields a hash that can be further modified. – Cacogenics

Answer 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", ...] }

Prepossess

This is elegant. – Grumpy

Answer 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.

Scandium

Answer 6

Check out the addressable gem - a popular replacement for Ruby's URI module that makes query parsing easy:

require "addressable/uri"
uri = Addressable::URI.parse("http://www.example.com/something?param1=value1&param2=value2&param3=value3")
uri.query_values['param1']
=> 'value1'

(It also apparently handles param encoding/decoding, unlike URI)

Minim

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. – Ard

Answer 7

Using CGI might be an outdated approach with Ruby 2.7/3.

Here's a neat way to do this with URI:

uri = URI.parse 'https://duckduckgo.com/?q=ruby+programming+language'
params = Hash[URI.decode_www_form uri.query]
# => {"q"=>"ruby programming language"} 

Biltong

Look, no additional libraries needed 👍 – Giesser

Answer 8

you can also use this method

require 'uri'
require 'cgi'
uri = URI("https://example.com/?query=1&q=2&query=5")
a = CGI::parse(uri.query)
puts a                   #=> {"query"=>["1", "5"], "q"=>["2"]}
puts a["query"].to_s     #=> ["1", "5"]
puts a["query"][0]       #=>  1
puts a["query"][1]       #=>  5
puts a["q"][0]           #=>  2

its safe and much easier

Nedranedrah

Answer 9

Sadly both the URI and addressable libraries break when attempting to extract query params from buggy URLs. E.g. this breaks both:

http://localhost:4300/webapp/foo/#//controller/action?account=001-001-111&email=john%40email.com

Building on Arthur / Levi's solution, with url.split("?").try(:last) you can grab just the query param portion of the URL, and use Rack::Utils.parse_nested_query to parse that string of parameters into a hash.

Or in full:

Rack::Utils.parse_nested_query(url.split("?").try(:last))

returning in my example:

{"account": "001-001-111", "email": "[email protected]"}

Ard

Answer 10

The above answers are very well written and they serve the purpose, however I tried some query manipulation and wanted to share here. So, here is my take:

   URI("http://example.com?par=hello&par2=bye").query.split('&').map { |param| {query_param: param.split('=')[0] , value: param.split('=')[1]}  }

It serves the purpose and return an array of objects for each query param. Having said that, please keep in mind the COC principle of ROR.

Ralph

Answer 11

In your Controller, you should be able to access a dictionary (hash) called params. So, if you know what the names of each query parameter is, then just do params[:param1] to access it... If you don't know what the names of the parameters are, you could traverse the dictionary and get the keys.

Some simple examples here.

Virgy

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