Load associations to one level while conditionally sideloading associations in Active model serializers

[vamsi-krishna-E0029]

This ain't an issue frankly speaking. May be a tailored feature request. Tried my best to get this working but in vain.
Using AMS version 0.8.3.
I created a base_serializer.rb like this and extended the same.

class BaseSerializer < ActiveModel::Serializer
  def include_associations!
    if @options[:embed]
      embed = @options[:embed].split(',').map{|item| item.strip.to_sym}
      embed.each do |assoc|
        include! assoc if _associations.keys.include?(assoc)
      end
    end
  end
end

class EventSerializer < BaseSerializer
  attributes :id, :name
  has_many :organizers, serializer: OrganizerSerializer
  has_many :participants, serializer: ParticipantSerializer
end

class OrganizerSerializer < BaseSerializer
  attributes :id, :name
  has_many :related, serializer: RelatedSerializer
end

class ParticipantSerializer < BaseSerializer
  attributes :id, :name
  has_many :related, serializer: RelatedSerializer
end

class RelatedSerializer < BaseSerializer
  attributes :id, :name
  has_many :something, serializer: SomethingSerializer
end

and the index method in EventsController is written as

# GET /events?embed=organizers,participants
  def index
      @events = Event.all
      render json: @events, embed: params[:embed]
  end

With this I can get the :id and :name of events, organizers and participants. But, I want the attributes of related association as well. I don't need details of something serializer. I want to go till this level for each association. How can I achieve that?

[groyoh]

I'm not sure if this would work but have you tried embed=organizers,participants,related ?
I might have another solution but I need to try it first.

[vamsi-krishna-E0029]

Thanks @groyoh That works. I never thought of trying like that. But, when I query for events. I would just know that organizers and participants are the associations for that model. Is there any way where I can fetch the association of association objects which are included?

For eg: May be I confused you a lot...

Before I iterate,

  embed = @options[:embed].split(',').map{|item| item.strip.to_sym}
  embed.each do |assoc|
    include! assoc if _associations.keys.include?(assoc)
  end

So, in my case the embed variable would have organizers,participants. Can I know the associations of organizers and participants (related) before hand so that I can add them in the embed variable when I iterate?

I was able to get the associations when I iterate. But, I need them before iterations.

  embed = @options[:embed].split(',').map{|item| item.strip.to_sym}
  embed.each do |assoc|
    assoc_obj = include! assoc if _associations.keys.include?(assoc)
    # This gives me the required associations which need to be added. But, I need it before iteration.
    p assoc_obj.first._associations.keys.inspect if assoc_obj.present?
  end

Thanks once again for the suggested solution. That helped me move one step closer.

[groyoh]

Once again I'm not sure about the solution, but you could try:

embed = @options[:embed].split(',').map{|item| item.strip.to_sym}
embed.each do |name|
  next unless _associations.key?(name)
  assoc_serializer = _associations[name].options[:serializer]
  embed = @options[:embed]
  @options[:embed] = assoc_serializer._associations.keys.join(",")
  include! name
  @options[:embed] = embed
end

But you need to make sure there is no recursive relationship or you might get an infinite loop.
Do you need it for only one level e.g. organizers and participants or do you also need to get the associations of related?

[vamsi-krishna-E0029]

I don't need associations of RelatedSerializer. I just need attributes of RelatedSerializer.

The [:serializer] doesn't seem to work. Getting the following error.

undefined method `[]' for (subclass of ActiveModel::Serializer::Associations::HasMany):Class

[groyoh]

I have something in mind then, but I'll try it later and tell you if it works.

[groyoh]

My bad, I made a typo. I updated the snippet.

[groyoh]

Here is my final solution, I tested it and it work as expected:

class BaseSerializer < ActiveModel::Serializer
  def include_associations!
    @options[:embed_level] ||= 1
    return unless @options.key?(:embed) && @options[:embed_level] != 0
    embed = @options[:embed].split(',').map{|item| item.strip.to_sym}
    embed.each do |assoc|
      next unless _associations.key?(assoc)
      assoc_serializer = _associations[assoc].options[:serializer]
      embed = @options[:embed]
      embed_level = @options[:embed_level]
      @options[:embed_level] -= 1
      @options[:embed] = assoc_serializer._associations.keys.join(",")
      include! assoc
      @options[:embed] = embed
      @options[:embed_level] = embed_level
    end
  end
end

then in your controller:

render json: @events, embed: "organizers,participants", embed_level: 2

Then you can change the embed_level option to set how deep it should load associations.

[vamsi-krishna-E0029]

This is perfect @groyoh . Thanks a lot. May be I'm asking for too much now. It is a problem from my end actually. the assoc_serializer might be nil at times where we don't specify any serializer option to associations at times. As of now I added a present? check for assoc_serializer. What can I do in those cases? Do we have any option to fetch the serializer when no serializer option is provided?

Say something like

has_many :roles

This association actually uses the RoleSerializer by default way. I don't specify any serializer option here.

class BaseSerializer < ActiveModel::Serializer
  def include_associations!
    @options[:embed_level] ||= 1
    return unless @options.key?(:embed) && @options[:embed_level] != 0
    embed = @options[:embed].split(',').map{|item| item.strip.to_sym}
    embed.each do |assoc|
      next unless _associations.key?(assoc)
      assoc_serializer = _associations[assoc].options[:serializer]
      embed = @options[:embed]
      embed_level = @options[:embed_level]
      @options[:embed_level] -= 1
      @options[:embed] = assoc_serializer._associations.keys.join(",") if assoc_serializer.present?
      include! assoc
      @options[:embed] = embed
      @options[:embed_level] = embed_level
    end
  end
end

Well, with this solution you actually made my day...

[groyoh]

Do your models inherit from ActiveModel::Base?

[vamsi-krishna-E0029]

I think you meant ActiveRecord::Base. If thats the case yes. My db models inherit from ActiveRecord::Base and serializers from ActiveModel::Serializer

[groyoh]

Yes that's what I meant, typo again 😄. Try:

class BaseSerializer < ActiveModel::Serializer
    def include_associations!
      @options[:embed_level] ||= 0
      return unless @options.key?(:embed) && @options[:embed_level] != 0
      embed = @options[:embed].split(',').map{|item| item.strip.to_sym}
      embed.each do |assoc|
        next unless _associations.key?(assoc)
        assoc_serializer = serializer_for(assoc)
        next unless assoc_serializer
        embed = @options[:embed]
        embed_level = @options[:embed_level]
        @options[:embed_level] -= 1
        @options[:embed] = assoc_serializer._associations.keys.join(",")
        include! assoc
        @options[:embed_level] = embed_level
      end
    end

    def serializer_for(assoc)
      serializer = _associations[assoc].options[:serializer]
      return serializer if serializer
      assoc_value = send(assoc)
      Array(assoc_value).first.active_model_serializer
    end
  end
end

[vamsi-krishna-E0029]

Thanks again...I actually tried out this at first.

    def serializer_for(assoc)
      serializer = _associations[assoc].options[:serializer]
      return serializer if serializer
      assoc.to_s.classify.concat("Serializer").constantize
    end

which one would you prefer? I guess both should work.

[groyoh]

Take yours if that works for you! 😉 And please close the issue if it's all good.

[vamsi-krishna-E0029]

Ha Ha...LOL... Thanks a lot @groyoh That was really a timely help...

[joaomdmoura]

Great! I'm glad to see that you guys figured it out! I'm closing it for now! bte @ovamsikrishna give a try to 0.10.x version ;) and try to use JSON API 😄

[beauby]

Since #1158 / #1127 you can do stuff like include: '*.*.*' (which exactly includes 3 levels of nested relationships) in 0.10.x.