Model Association (Rails 5 API) I have a Character model that has a CharClass and ClassPerks child.

Currently I am duplicating my logic a lot by manually assigning data.

My Character index and create:

def index

    @campaign = Campaign.find_by_id(params[:campaign_id])
    @characters = @campaign.characters
    render json: {
        characters: @characters
    }
end

def create
    @campaign = Campaign.find_by_id(params[:campaign_id])
    @charClass = CharClass.find_by_id(params[:character_char_class_id])
    @character = @campaign.characters.new(character_params)
    @character.char_class_id = params[:character_char_class_id]

    if @character.save!
        render status: 201, json: {

            message: "Successfull added this character to the campaign!",
            character_name: @character.character_name + ' the ' + @charClass.class_name,
            character_class: @charClass.class_name,
            character_level: @character.character_level,
            character_experience: @character.character_experience,
            character_gold: @character.character_gold,
            character_perks: get_names(@character.character_perks),
            character_image: @character.character_image

        }
    else
        render status: 404, json: {
            message: "Something went wrong: Check line 24 of the Character Controller"
        }
    end
end


I am manually assigning character_class and character_image despite both of these ALWAYS being the same based on their character_class.

Inside of the character.rb I am doing this to assign them post-create:

    after_create :add_perks, :save_class

    def add_perks
        self.class_perks.each do |perk|
            self.character_perks.create(class_perk_id: perk.id)
        end
    end


    def save_class()
        case self.char_class_id
            when 1 # Mindthief
                self.character_image = "https://gloomhavenil.files.wordpress.com/2017/12/11849117_616974988445216_217288420_n.jpg?w=480"
                self.character_class = "Mindthief"
                self.save
            when 2 # Tinkerer
                self.character_image = "http://www.cephalofair.com/wp-content/uploads/2015/04/Quatryl-Tinkerer.jpg"
                self.character_class = "Tinkerer"
                self.save
            # when 'Sawbones'
            # else
        end
    end
end


It is working, but I am unsure how to do this better/appropriately. I removed useless fields but you'll see below I have the relations set up appropriately.

  create_table "char_classes", force: :cascade do |t|
    t.string "class_name"
    t.string "class_image"
    t.string "class_perks"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

 create_table "characters", force: :cascade do |t|
    t.string "character_class"
    t.string "character_image"
    t.integer "char_class_id"
    t.index ["campaign_id"], name: "index_characters_on_campaign_id"
    t.index ["char_class_id"], name: "index_characters_on_char_class_id"
  end


I can do Character.first.char_class.class_name and I will get the appropriate result; so I am back to assuming this method I'm following is very incorrect.
You need to use ActiveModelSerializers (AMS) to serialize your json responses based upon the instances of your class.

class CampaignsController &lt; ApplicationController
  def index
    render json: { characters: campaign.characters }
  end

  def create
    @character = campaign.characters.new(character_params.merge(char_class_id: char_class.id))

    if @character.save!
        render json: @character, serializer: CharacterSerializer, status: 201 # This should automatically be formatted by AMS
    else
        not_found('Something went wrong: Check line 24 of the Character Controller')
    end
  end

  private

  def campaign
    @campaign ||= Campaign.find_by_id(params[:campaign_id])
  end

  def char_class
    @charClass ||= CharClass.find_by_id(params[:character_char_class_id])
  end
end


This is how you AMS class for Character class should look like

class CharacterSerializer &lt; ActiveModel::Serializer
  attributes :message, :character_name, :character_class, :character_level, :character_experience, :character_gold, :character_perks, :character_image

  def message
    'Successfull added this character to the campaign!'
  end

  def character_name
    return object.character_name + ' the ' + character_class # check the associations
  end

  def character_class
    object.charClass.class_name
  end

  def character_perks
    # Unsure what this get names methods does so im leaving it for you to refactor
    get_names(object.character_perks),
  end

end


Also add this to your ApplicationController

class ApplicationController &lt; ActionController::Base

  # Add this to your application controller

  def not_found(message = nil)
    render json: { message }, status: 404
  end

end


I'll update the refactored model class based upon your info soon. Hope this helps for now.