Specify association serializer with conditional?

[eliduke]

Hello AMSers!

I need some help and I hope I have come to the right place.

I am using AMS 0.8.3 and I am trying to use a conditional in a serializer to specify which serializer to use for a certain association. The standard json end point has a list of users with basic information. Then I want to have an "export" end point where more detailed user information would be output into a CSV or something like that.

Here's what I have so far...

class PrizeController < ApplicationController

def entrants
  render json: @prize, export: true, serializer: PrizeEntrantsSerializer
end

I'm passing in the export: true option thinking that I can use that in the conditional.

class PrizeEntrantsSerializer < ActiveModel::Serializer

  attributes :id, :event, :event_prize_type,
  has_many :entrants, serializer: which_serializer

  def which_serializer
    @options[:export] == true ? PrizeEntrantExportSerializer : PrizeEntrantSerializer
  end

end

That didn't work. I get undefined local variable or method 'which_serializer', so I tried this:

class PrizeEntrantsSerializer < ActiveModel::Serializer

  attributes :id, :event, :event_prize_type

  if @options[:export] == true
    has_many :entrants, serializer: PrizeEntrantExportSerializer
  else
    has_many :entrants, serializer: PrizeEntrantSerializer
  end

end

That doesn't work either. I get undefined method '[]' for Nil Class. I am able to pass in the @options successfully because I tested it out by adding as an attribute and it does return correctly. Is it just not possible to have conditionals in a serializer?

Thanks for your help!

[mehlah]

Hello guys,

I created a Rails app that reproduces what's described by @eliduke https://github.com/mehlah/ams-issue-825/

I'm suggesting a fix at #865, to support Symbols for :serializer option, that refers to a method to call.
I'm making myself familiar with AMS code and architecture, so I'm not sure this is the right direction. If so, I think we should support passing a Proc too.
@joshsmith thoughts?
Is this something to port to 0.10.x/master?

[kurko]

@eliduke has_many is a class method whereas which_serializer is an instance method. Try def self. which_serializer instead. Should work.

[beauby]

@eliduke Did @kurko's suggestion help?

[eliduke]

@beauby Thanks for pinging me again on this. In the end I switched things up and found a different solution, but now that this is back in my brain I will take a look and see if @kurko's suggestion works.

[eliduke]

I came across another instance where I could use a conditional serializer, and so I was very excited to give this a shot again. Unfortunately, it didn't work. Keep in mind, that I am using AMS 0.8.3.

module Adm
  class PostSerializer < ActiveModel::Serializer
    attributes :id, :title, :body
    has_many :authors, serializer: authors_serializer

    def authors
      object.authors
    end

    def self.authors_serializer
      if object.authors.first.class.class_name == "EventSpeaker"
        Adm::EventSpeakerSerializer
      else
        Adm::PostContributorSerializer
      end
    end
  end
end

And that gives me this error:

undefined local variable or method `authors_serializer' for Adm::PostSerializer:Class

That authors method just checks a couple things and conditionally returns Event Speakers or Post Contributors.

[NullVoxPopuli]

@eliduke just curious, what's keeping you on 0.8.3? 0.10 has some really nice syntax that would help clean this up (cause @beauby is awesome)

[eliduke]

@NullVoxPopuli I have been waiting for it to be an official release. As far as I know, it's still just a release candidate. Has 0.10 been officially released yet?

[NullVoxPopuli]

it has not been released yet, but AMS is on the 3rd release candidate. so, you could use the tag v0.10.0.rc3 in your gemfile, or the branch master.

It's not 100% guaranteed, but master is raaaaaarrreeelllyy ever has any failing tests (and it's usually because of an oversight when merging something else)

[eliduke]

Okay. So, let's say that I can convince my team that we should upgrade, how would 0.10 make what I want to accomplish here easier? You say that there's some nice syntax that would help clean up what I want to do.

[beauby]

@eliduke In 0.10 the serializer lookup is made in such a way that if your author is an instance of EventSpeaker and you have defined an EventSpeakerSerializer, then that's what will be used.

[NullVoxPopuli]

👍