Standard way for Rails to parse array query params without using brackets in the URL?

Question

I want a resource URI to look like this:

https://domain.tld/resource?param=foo&param=bar&param=baz

But Rails requires array query params to use the square bracket notation. Before URL escaping, the Rails equivalent of the above URI looks like this:

https://domain.tld/resource?param[]=foo&param[]=bar&param[]=baz

I can manually wrangle request.url inside of my controller, but I'd rather not do this ad-hoc if I can help it. Is there a standard way to support the first style of URI in Rails?

Danil Speransky · Accepted Answer · 2014-02-07 18:56:28Z

3

No standard way.

Any way I think it is not good idea to change it for whole rails application, because it breaks conventions (and probably some helpers).

edited Feb 7, 2014 at 18:56

answered Feb 7, 2014 at 18:42

Danil Speransky

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5 Comments

Dave Newton Over a year ago

Several frameworks use that to indicate a collection of parameters, e.g., an array or a list.

GrooveStomp Over a year ago

I agree with @DaveNewton here, as does the Wikipedia article. "While there is no definitive standard, most web frameworks allow multiple values to be associated with a single field." en.wikipedia.org/wiki/Query_string

Dave Newton Over a year ago

@SperanskyDanil Meh; AFAIC the important part of the answer is the "no standard way" part--I was just pointing out that the additional part isn't really correct. Not so wrong as to warrant downvotes IMO.

GrooveStomp Over a year ago

@SperanskyDanil I was a bit liberal with the downvote. Unfortunately, you can't "un-downvote." :\ I could upvote to neutralize.

GrooveStomp Over a year ago

@SperanskyDanil Good approach! :) I like your edited answer much better. FYI - my changes will be restricted to a specifically scoped group of controllers.

Aaron · Accepted Answer · 2024-06-05 14:39:01Z

`tl;dr`

You can accomplish this with standard Ruby tools using the raw URL. I have the following helper method in my ApplicationController to support this:

# Support for flat array params, `URI#query` can return `nil`
def raw_params = CGI.parse(URI(request.url).query || "")

Major Caveat

I must support this as it's a requirement of many third party APIs. However, unless you have a compelling business need, I'd echo the strong recommendations to not deviate from conventions. It requires more work down the line and copious comments so I don't forget why I'm doing goofy looking things when I revisit the code.

Examples

Faraday requires a connection specifically for this:

Faraday.new(request: {params_encoder: Faraday::FlatParamsEncoder})

WebMock needs to be configured to support this:

WebMock::Config.instance.query_values_notation = :flat_array

Stubs cannot use the more descriptive syntax and work off a raw string:

# This is my working test because…
stub_request(:get, "https://domain.tld/resource?param=foo&param=bar")
  .to_return(…)

# this won't work as `WebMock will add `[]`s
stub_request(:get, "https://domain.tld/resource")
  .with(query: {param: ["foo", "bar"]})
  .to_return(…)

And finally, query params need to be manually constructed differently:

# I need to do
URI.encode_www_form({param: ["foo", "bar"]}) #=> "param=foo&param=bar"

# vs. pure Rails
{param: ["foo", "bar"]}.to_query #=> param%5B%5D=foo&param%5B%5D=bar

None of this is truly abhorrent and I still sleep well at night but conventions make things so much easier to work with and vastly decrease your cognitive load when coding.

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