ActiveModel::Serializer has_many hash of objects - ruby-on-rails

Question

I've got an ActiveModel::Serializer question for the experts. Lets say I have the following JSON output where the root element is a SurveyInvite object. Currently the question_answers hash key is just an array of QuestionAnswer objects. How can I make it so that question_answers is a hash of QuestionAnswer objects where the keys are QuestionAnswer.question.id?
{
id: 1,
email: "foo#example.com",
status: "Submitted",
created_at: "10:57AM Sep 1, 2015",
date_submitted: "10:58AM Sep 1, 2015",
survey_response: {
id: 1,
survey_invite_id: 1,
name: "Foo Bar",
title: "Ninja",
published: true,
created_at: "10:58AM Sep 1, 2015",
updated_at: " 3:42PM Sep 2, 2015",
question_answers: [
{
id: 1,
survey_response_id: 1,
mini_post_question_id: 20,
answer: "What is the answer?",
created_at: "2015-09-14T14:59:39.599Z",
updated_at: "2015-09-14T14:59:39.599Z"
},
{
id: 2,
survey_response_id: 1,
mini_post_question_id: 27,
answer: "What is the answer?",
created_at: "2015-09-15T20:58:32.030Z",
updated_at: "2015-09-15T20:58:32.030Z"
}
]
}
}
Here is my SurveyResponseSerializer:
class SurveyResponseSerializer < ActiveModel::Serializer
attributes :id, :survey_invite_id, :name, :title, :published, :created_at, :updated_at
has_many :question_answers
def created_at
object.created_at.in_time_zone("Eastern Time (US & Canada)").strftime("%l:%M%p %b %w, %Y")
end
def updated_at
object.updated_at.in_time_zone("Eastern Time (US & Canada)").strftime("%l:%M%p %b %w, %Y")
end
end
Basically, I want the question_answers key value to be a hash of QuestionAnswer objects where the keys are the question id QuestionAnswer.question_id. I've looked through the docs and haven't turned up any examples of what I'm trying to do.
Update with solution:
So I came up with a solution that works for what I need, but I'd still like to know if there is a better way to do what I need. I wrote a method to generate the structure I need.
def question_answers
hash = {}
object.question_answers.each do |answer|
hash[answer.mini_post_question_id] = answer
end
hash
end
That yields the following:
question_answers: {
20: {
id: 1,
survey_response_id: 1,
mini_post_question_id: 20,
answer: "Test?",
created_at: "2015-09-14T14:59:39.599Z",
updated_at: "2015-09-14T14:59:39.599Z"
},
27: {
id: 2,
survey_response_id: 1,
mini_post_question_id: 27,
answer: "Blarg!",
created_at: "2015-09-15T20:58:32.030Z",
updated_at: "2015-09-15T20:58:32.030Z"
}
}

Answer 1

I don't think ActiveModelSerializers has an idiomatic way to present a has_many association as a hash, but you can do it with a one-liner:
def question_answers
object.question_answers.index_by(&:id)
end