今回の実装ポリシーについて

設計の健全性よりもRailsらしいことを追求してみました。
設計の健全性の話をすると、データを取得するクラスとWebAPIにリクエストを行うクラスを分けるべきで、それはもうActiveModelを使ってはいけないことになり、今回の趣旨に反するので。

実装の全文だったり、サンプルはGistにも掲載しているので読みにくければこちらもご覧ください。

base.rb

GitHub Gist: instantly share code, notes, and snippets.

ベースモデルの実装及び解説

require_relative 'errors'

module ApiModel
  module Base
    extend ActiveSupport::Concern
    include ActiveModel::Model
    include ActiveModel::Attributes
    include ActiveModel::Serializers::JSON

    included do
      private 

      attr_accessor :response
    end

    class_methods do
      def api_url
        'http://localhost:3000'
      end

      def client
        Faraday.new(url: api_url) do |faraday|
          faraday.adapter Faraday.default_adapter
          faraday.request :json
          faraday.response :json, parser_options: { symbolize_names: true }
        end
      end

      def raise_api_exception(response)
        case response.status
        when 404
          raise ApiNotFound.new(response), "Record not found"
        when 422
          raise ApiInvalidError.new(response), "Invalid data"
        when 400..499
          raise HttpClientError.new(response), "Client error"
        when 500..599
          raise HttpServerError.new(response), "Server error"
        else
          raise ApiError.new(response), "Api Error"
        end
      end

      def request(method, *args, &block)
        response = client.public_send(method, *args) do |req|
          yield req if block_given?
        end
        if response.success?
          response
        else
          raise_api_exception(response)
        end
      end
    end

    def has_error?
      errors.any?
    end

    def validate!
      raise RecordInvalidError.new(self) unless valid?
    end

    private

    def request(method, *args, &block)
      @response = self.class.client.public_send(method, *args) do |req|
        yield req if block_given?
      end
      if response.success?
        true
      else
        handle_api_errors
      end
    end

    def request!(method, *args, &block)
      @response = self.class.client.public_send(method, *args) do |req|
        yield req if block_given?
      end
      if response.success?
        self
      else
        raise_api_exception
      end
    end

    def raise_api_exception
      case response.status
      when 404
        raise ApiNotFound.new(response), "Record not found"
      when 422
        add_api_errors
        raise RecordInvalidError.new(self, response)
      when 400..499
        raise HttpClientError.new(response), "Client error"
      when 500..599
        raise HttpServerError.new(response), "Server error"
      else
        raise ApiError.new(response), "Api Error"
      end
    end

    def handle_api_errors
      raise_api_exception
    rescue RecordInvalidError
      false
    end

    def add_api_errors
      return unless response.status == 422
    
      error_message = :unknown_error

      # Get the custom error message if available, otherwise use the default message
      custom_error_key = "activemodel.errors.models.#{self.class.name.underscore}.response.#{error_message}"
      common_error_key = "activemodel.errors.api_record.response.#{error_message}"
      error_message_text = I18n.t(custom_error_key, default: I18n.t(common_error_key))

      errors.add(:response, error_message_text)

      error_response = response.body
      if error_response.is_a?(Hash)
        error_response.each do |key, error_details|
          error_details.each do |message|
            errors.add(key, message)
          end
        end
      end
    end
  end
end

module ApiModel
  class RecordInvalidError < StandardError
    attr_reader :record, :response

    def initialize(record, response = nil)
      @record = record
      @response = response
      message = "Validation failed: #{record.errors.full_messages.join(', ')}"
      super(message)
    end
  end

  class ApiError < StandardError
    attr_reader :response

    def initialize(response)
      @response = response
    end
  end

  class HttpClientError < ApiError; end
  class HttpServerError < ApiError; end
  class ApiNotFound < HttpClientError; end
end

基本的なモジュールの利用方法

module Api
  class Payment
    include ApiRecord::Base

    attribute :user, :user
    attribute :card_number, :integer

    validates :card_number, presence: true, numericality: { only_integer: true, greater_than: 0 }
    validates :user, presence: true

    def save
      return false unless valid?

      params = {
        user_id: user.id,
        card_number: card_number
      }

      request(:post, "/users/#{user.id}/payments", params)
    end

    def save!
      validate!

      params = {
        user_id: user.id,
        card_number: card_number
      }

      request!(:post, "/users/#{user.id}/payments", params)
    end

  end
end

class Payment::AuthorizeController < ApplicationController
   def create
     payment = Api::Payment.new(card_number: params[:card_number], user: user)
     if payment.save
       head 204
     else 
       render json: { payment.errors }, status: 422
     end
   end
end

class Payment::AuthorizeController < ApplicationController
   def create
     payment = Api::Payment.new(card_number: params[:card_number], user: user)
     payment.save!
     head 204
   end
end

CRUDを実装する場合

module ApiModel
  Relation = Struct.new(:data, :response)
end

CRUDは長いので、こちらのGistからApi::Productクラスを読んでみてください。

base.rb

GitHub Gist: instantly share code, notes, and snippets.

CRUDの利用サンプル

実装したモデルをControllerで呼び出す際のサンプルコードを、
Controllerのサンプルコードだけ抜粋しておきました。
これはまんまRailsですねぇ。。。

class ProductsController < ApplicationController
   before_action :set_product, only: [:show, :update, :destroy]
   
   def index
     @products = Api::Product.index.data
   end
   
   def show
   end
   
   def create
     @product = Api::Product.new(params)
     if @product.save
       render :show, status: 201
     else
       render json: { @product.errors }, status: 422     
     end
   end
   
   def update
     if @product.update(params)
       render :show
     else 
       render json: { @product.errors }, status: 422
     end
   end
   
   def destroy
     @product.destroy
     head :no_content
   end
   
   private 
   
   def set_product
     @product = Api::Product.find(params[:id])
   end
   
   # Only allow a list of trusted parameters through.
   def product_params
     params.require(:product).permit(:title)
   end
end

工夫したところ

作ってみてどうだったか