Rails String Replace URL Parameters

Question

Let's say I have a string like:

url = "https://example.com/user/tr_auth.php?key=34432&cmp_id=344&tr_id={user_id}"

I want to update the cmp_id=344 to be say cmp_id=44553. What's the best way to accomplish this? I can't gsub per say because I don't know what cmp_id might be equal, only that it will be a URL parameter in the string.

It seems like I want to do something like

uri = URI.parse(url)
params = CGI.parse(uri.query)

But then, how do I re-build the string swapping out the cmp_id parameter to be 44553?

Thanks!

Simone Carletti · Accepted Answer · 2017-01-31 19:38:48Z

27

If you are dealing with a web application (and/or Rails as the tag seems to indicate), then you certainly have Rack available. Rack::Utils has methods to parse and build a query.

url = "https://example.com/user/tr_auth.php?key=34432&cmp_id=344&tr_id={user_id}"
uri = URI.parse(url)

query = Rack::Utils.parse_query(uri.query)
# => {"key"=>"34432", "cmp_id"=>"344", "tr_id"=>"{user_id}"}

# Replace the value
query["cmp_id"] = 44553

uri.query = Rack::Utils.build_query(query)
uri.to_s
# => "https://example.com/user/tr_auth.php?key=34432&cmp_id=44553&tr_id=%7Buser_id%7D"

Also note that Rack, by default, escapes the query.

answered Jan 31, 2017 at 19:38

Simone Carletti

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Florin Ionita · Accepted Answer · 2017-01-31 19:54:11Z

2

url = "https://example.com/user/tr_auth.php?key=34432&cmp_id=344&tr_id={user_id}"
uri = URI.parse(url)
params = CGI.parse(uri.query)
params['cmp_id'] = 44553

new_str = uri.host + uri.path + '?' + params.to_query

answered Jan 31, 2017 at 19:54

Florin Ionita

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Dmitry Kukhlevsky · Accepted Answer · 2017-01-31 19:42:31Z

1

First, you can parse the url for params:

require 'cgi'
url = 'https://example.com/user/tr_auth.php?key=34432&cmp_id=344&tr_id={user_id}'
string_params = url.split('?')[1]
hash = CGI::parse(string_params)

Then you can iterate the hash by keys and change values:

hash.keys.each {|key| hash[key]='new value'}
url_params = hash.to_param

answered Jan 31, 2017 at 19:42

Dmitry Kukhlevsky

2762 silver badges6 bronze badges

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