What is the most elegant way in Ruby to remove a parameter from a URL?

I would like to take out a parameter from a URL by its name without knowing which parameter it is, and reassemble the URL again.

I guess it is not that hard to write something on my own using CGI or URI, but I imagine such functionality exists already. Any suggestions?

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Here's a clean one if your url is a string:
```
def remove_param(url, param_name)
uri = URI(url)
params = []
URI.decode_www_form(uri.query || '').each do |param|
next if param[0] == param_name

params << param
end
uri.query = URI.encode_www_form(params)
uri.to_s
end
```

note: you could use this to remove a param with a specific value by changing:
```
def remove_param(url, param_value)
```
and
```
next if param[1] == param_value
```

If you don't want to include an extra Gem and if you don't want nasty Regex, here's my prefered way:

require 'cgi'
require 'uri'

url = "http://example.com/path?param1=one&param2=2&param3=something3"

uri = URI(url) #=> #<URI::HTTP:0x007fbe25141a78 URL:http://example.com/path?param1=one&param2=2&param3=something3>
params = Rack::Utils.parse_nested_query(uri.query || "") #=> {"param1"=>["one"], "param2"=>["2"], "param3"=>["something3"]}
params.delete('param1') #=> ["one"]
uri.query = URI.encode_www_form(params) #=> "param2=2&param3=something3"

uri.to_s #=> "http://example.com/path?param2=2&param3=something3"

**Note,** choose wisely:

CGI.parse('a=b&a=c') #=> {"a"=>["b", "c"]}
Rack::Utils.parse_nested_query('a=b&a=c') #=> {"a"=>"c"}

And:

URI.encode_www_form({ a: :b, c: { d: 2 }}) #=> "a=b&c=%7B%3Ad%3D%3E2%7D"
{ a: :b, c: { d: 2 }}.to_query #=> "a=b&c%5Bd%5D=2"

The _addressable_ gem will do this nicely; please see the superior answer by _The Tin Man_. But if you want to roll your own, here's how. The only claim this code has to elegance is that it hides the ugly in a method:

#!/usr/bin/ruby1.8

def reject_param(url, param_to_reject)
# Regex from RFC3986
url_regex = %r"^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?$"
raise "Not a url: #{url}" unless url =~ url_regex
scheme_plus_punctuation = $1
authority_with_punctuation = $3
path = $5
query = $7
fragment = $9
query = query.split('&').reject do |param|
param_name = param.split(/[=;]/).first
param_name == param_to_reject
end.join('&')
[scheme_plus_punctuation, authority_with_punctuation, path, '?', query, fragment].join
end

url = "http://example.com/path?param1=one&param2=2&param3=something3"
p url
p reject_param(url, 'param2')

# => "http://example.com/path?param1=one&param2=2&param3=something3"
# => "http://example.com/path?param1=one&param3=something3"

One line should be enough:

url.sub(/\?param_to_remove=[^&]*/, '?').sub(/\&param_to_remove=[^&]*/, '').sub(/\?$/,'')

I prefer to use:

require 'addressable/uri'

uri = Addressable::URI.parse('http://example.com/path?param1=one&param2=2&param3=something3')

params = uri.query_values #=> {"param1"=>"one", "param2"=>"2", "param3"=>"something3"}
params.delete('param1') #=> "one"
uri.query_values = params #=> {"param2"=>"2", "param3"=>"something3"}

uri.to_s #=> "http://example.com/path?param2=2&param3=something3"

Maybe a little off-topic, but for anyone who's attempting to do this in the context of a rails app you can simply do:

url_for(params.except(:name_of_param_to_delete))

N.B. Tested in rails v2.3.9.

I came up with something like this

def uri_remove_param(uri, params = nil)
return uri unless params
params = Array(params)
uri_parsed = URI.parse(uri)
return uri unless uri_parsed.query
escaped = uri_parsed.query.grep(/&/).size > 0
new_params = uri_parsed.query.gsub(/&/, '&').split('&').reject { |q| params.include?(q.split('=').first) }
uri = uri.split('?').first
amp = escaped ? '&' : '&'
"#{uri}?#{new_params.join(amp)}"
end