Parsing collections from HAL API's

[Steve Hoeksema]

Hi all,

I'm trying to save some time when querying a third party API that claims to be HAL.

https://gist.github.com/steveh/ab975e70333d6aabad8f

A (truncated) API response is in the heredoc.

How can I parse that JSON as a collection of objects? I can't get more than an empty array.

cheers!

[Nick Sutterer]

Hi Steve,

check out the docs! https://github.com/apotonick/roar#nesting-1

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[Steve Hoeksema]

Hi Nick,

I've read through the docs and done some experimenting. That section seems to be about output, I'm talking about input.

The only examples I've seen are about parsing collections that are attached to an entity (like a has_many), I can't find out how to parse a collection with no parent - e.g. a list, like my attached example.

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[Nick Sutterer]

Ah, I missed this. You have to use a lonely collection representer that uses the actual representer you wrote for items: https://github.com/apotonick/representable#lonely-collections

You should also be able to use for_collection with your ServiceRepresenter itself: https://github.com/apotonick/representable#representing-singular-models-and-collections

ServiceRepresenter.for_collection.prepare([]).from_json ".."

[Nick Sutterer]

For a better understanding, the following two calls are identical:

ServiceRepresenter.for_collection.prepare([]).from_json ".."

[].extend(ServiceRepresenter.for_collection).from_json ".."

[Nick Sutterer]

Anyway, what you really wanna do (and that is documented in the README) is this.

module ServiceRepresenter

  include Roar::Representer::JSON::HAL
  collection :services, embedded: true do
    property :id
  end
end


The incoming document is a valid HAL document, so you need a HAL representer!  One requirement here, though. The represented object needs a services accessor, though.

OpenStruct.new.extend(ServiceRepresenter).from_json "..".services #=> [..]

This is the generic way using the HAL representer. I can't think of a way to tell Roar to parse the embedded services keys as a lonely collection. Does the above stuff work of for you?