ROR: Serializing output for multiple objects - ruby-on-rails

Question

I am learning rails, and using active_model_serializers gem.
I need to get the customized output in JSON from two different tables. Here is an example
car: id, name, color, size, shape, date...
battery: id, car_id, price, weight, name, date...
class battery < ApplicationRecord
belongs_to :car
end
query I ran is
## This is sample query will not work
Car.includes(:battery).where(car: {color: red}).where(date >= 'blah')
I have three hashes in calculated in my controller
#cars_controller.rb
available_cars ={
available_cars:[{id:id,
name:name,
color:color,
size:size,
date:date..
}]
}
available_battries = {
available_batteries:[{id:id,
card_id:car_id,
price:price,
weight:weight,
name:name,
date:date..
}]
}
cars_with_battires = {
cars_with_battry: [{id:id,
name:name,
color:color,
size:size,
date:date..},
battries:[{id: 1,
name: name1
},
{id: 2,
name: name2
}
]
]}
render json: {
available_cars: available_cars,
available_batteries: available_batteries,
cars_with_battry: cars_with_battry }
serializer: CarIndexListSerializer }
This is my serializer file looks like and I need to fill those functions
#car_index_list_serializer.rb
class CarIndexListSerializer < ActiveModel::Serializer
attributes :available_cars,
:available_batteries,
:cars_with_battry
def available_cars
#todo?
end
def available_batteries
#todo?
end
def cars_with_battry
#todo?
end
I can just remove the fields I dont want and return the result in JSON but I want to use active_model_serializers to return it in following format.
{
available_cars:[{id: 1, name:name1, size: abc}],
available_batteries:[{id: 1, name: name1}],
cars_with_battry:[{id: 1, name:name1, size: abc,
battries:[{id: 1, name: name1}]
}]
}
if any of the hash is empty, I do not want to show it in the results

Answer 1

result = {}
available_cars = Car.where xxx
if available_cars.count.positive?
result[:available_cars] = available_cars.map {|car| CarSerializer.new(car).as_json }
end
# do the same thing for available battery and car with battery
render json: result
just a rough idea
Update
Usually for #index action on controller, it render list of resources
so CarIndexListSerializer is not required
What you have to create is two serializers:
car serializer
battery serializer
even you can add a relationship data to your car serializer
class CarSerializer < ActiveModel::Serializer
has_many :batteries
end
class Car < ApplicationRecord
has_many :batteries
end
so when you call this
car = Car.last
CarSerializer.new(car).as_json
it would return the car and batteries data
don't forget to create BatterySerializer too