How to accept multiple URL parameters in Rails with the same key?

Question

In Rails, when you want to send a list of values through a single array parameter, you usually do so by suffixing the URL parameter key with []. For example, the query string ?foo[]=1&foo[]=2&foo[]=3 is parsed as

params = { "foo" => [ 1, 2, 3 ] }

But for ?foo=1&foo=2&foo=3, only the last argument shows up in the params hash:

params = { "foo" => 3 }

Everything's fine while you can control the URL format; you can just use the [] syntax. But what if the URL is constructed by a remote system that you cannot influence, and that insists on the second format? How can one get the arguments unpacked properly?

You are going to need to parse the URI manually, you can use [URI::decode_www_form](http://ruby-doc.org/stdlib-1.9.3/libdoc/uri/rdoc/URI.html#method-c-decode_www_form) — max, Jun 03 '15 at 10:00
go through the https://github.com/sporkmonger/addressable - replacement for Ruby's URI module. — Pardeep Dhingra, Jun 03 '15 at 10:09

score 1 · Answer 1 · answered Jun 03 '15 at 11:07

Using the hint from @maxcal I came up with this solution (to avoid adding yet more gems to this completely bloated app that I'm working on):

current_query_string = URI(request.url).query
foo_values = URI::decode_www_form(current_query_string).
  select { |pair| pair[0] == "foo" }.
  collect { |pair| pair[1] }

How to accept multiple URL parameters in Rails with the same key?

1 Answers1