Custom field in ActiveModel Serializer with another serializer

Question

I have User model with has_many :sessions. But for one particular request I want to send only one session based on request device platform (iOS, Android).

The problem is that I have separate UserSerializer and UserSessionSerializer and I want to pass UserSessionSerializer as option in UserSerializer for :session field. Like this:

# UsersController
render json: @user, serializer: UserSerializer, session: @session # @user's session founded by platform

# UserSerializer
attributes :id, :email, :username, :session

def session
  @instance_options[:session], serializer: UserSessionSerializer
end

It is impossible, because I can pass serializer only in has_one and has_many as I understand. But I don't want to render all user sessions in JSON with has_many, only founded one.

Thanks for any help!

Answer 1

Your code is good just use UserSessionSerializer.new instead of serializer: UserSessionSerializer

render json: { user: UserSerializer.new(@user, session: @session) }

attributes :id, :email, :username, :session

def session
  UserSessionSerializer.new(self.instance_options[:session]) if self.instance_options[:session].present?
end