GraphQL on Rails——至臻

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# app/graphql/mutations/add_item_mutation.rb

module Mutations
  class AddItemMutation < Mutations::BaseMutation
    # ...

    def resolve
      if context[:current_user].nil?
        raise GraphQL::ExecutionError,
              "You need to authenticate to perform this action"
      end

      save_item
    end
  end
end

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# app/graphql/mutations/base_mutation.rb

module Mutations
  class BaseMutation < GraphQL::Schema::Mutation
    def check_authentication!
      return if context[:current_user]

      raise GraphQL::ExecutionError,
            "You need to authenticate to perform this action"
    end
  end
end

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# app/graphql/types/validation_errors_type.rb

module Types
  class ValidationErrorsType < Types::BaseObject
    field :details, String, null: false
    field :full_messages, [String], null: false

    def details
      object.details.to_json
    end
  end
end

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# app/graphql/mutations/add_item_mutation.rb

module Mutations
  class AddItemMutation < Mutations::BaseMutation
    argument :title, String, required: true
    argument :description, String, required: false
    argument :image_url, String, required: false

    field :item, Types::ItemType, null: true
    field :errors, Types::ValidationErrorsType, null: true # this line has changed

    def resolve(title:, description: nil, image_url: nil)
      check_authentication!

      item = Item.new(
        title: title,
        description: description,
        image_url: image_url,
        user: context[:current_user]
      )

      if item.save
        { item: item }
      else
        { errors: item.errors } # change here
      end
    end
  end
end

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# app/models/item.rb

class Item < ApplicationRecord
  belongs_to :user

  validates :title, presence: true
  validates :description, length: { minimum: 10 }, allow_blank: true
end

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# app/graphql/mutations/sign_in_mutation.rb

module Mutations
  class SignInMutation < Mutations::BaseMutation
    argument :email, String, required: true

    field :token, String, null: true
    field :user, Types::UserType, null: true

    def resolve(email:)
      user = User.find_by!(email: email)

      token = Base64.encode64(user.email)

      {
        token: token,
        user: user
      }
    rescue ActiveRecord::RecordNotFound
      raise GraphQL::ExecutionError, "user not found"
    end
  end
end

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# app/graphql/types/item_attributes.rb

module Types
  class ItemAttributes < Types::BaseInputObject
    description "Attributes for creating or updating an item"

    argument :title, String, required: true
    argument :description, String, required: false
    argument :image_url, String, required: false
  end
end

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# app/graphql/mutations/add_item_mutation.rb

module Mutations
  class AddItemMutation < Mutations::BaseMutation
    argument :attributes, Types::ItemAttributes, required: true # new argument

    field :item, Types::ItemType, null: true
    field :errors, Types::ValidationErrorsType, null: true # <= change here

    # signature change
    def resolve(attributes:)
      check_authentication!

      item = Item.new(attributes.to_h.merge(user: context[:current_user])) # change here

      if item.save
        { item: item }
      else
        { errors: item.errors }
      end
    end
  end
end

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# app/graphql/types/subscription_type.rb

module Types
  class SubscriptionType < GraphQL::Schema::Object
    field :item_added, Types::ItemType, null: false, description: "An item was added"

    def item_added; end
  end
end

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# app/graphql/martian_library_schema.rb

class MartianLibrarySchema < GraphQL::Schema
  use GraphQL::Subscriptions::ActionCableSubscriptions

  mutation(Types::MutationType)
  query(Types::QueryType)
  subscription(Types::SubscriptionType)
end

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# app/channels/graphql_channel.rb

class GraphqlChannel < ApplicationCable::Channel
  def subscribed
    @subscription_ids = []
  end

  def execute(data)
    result = execute_query(data)

    payload = {
      result: result.subscription? ? { data: nil } : result.to_h,
      more: result.subscription?
    }

    @subscription_ids << context[:subscription_id] if result.context[:subscription_id]

    transmit(payload)
  end

  def unsubscribed
    @subscription_ids.each do |sid|
      MartianLibrarySchema.subscriptions.delete_subscription(sid)
    end
  end

  private

  def execute_query(data)
    MartianLibrarySchema.execute(
      query: data["query"],
      context: context,
      variables: data["variables"],
      operation_name: data["operationName"]
    )
  end

  def context
    {
      current_user_id: current_user&.id,
      current_user: current_user,
      channel: self
    }
  end
end

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# app/channels/application_cable/connection.rb

module ApplicationCable
  class Connection < ActionCable::Connection::Base
    identified_by :current_user

    def connect
      self.current_user = current_user
    end

    private

    def current_user
      token = request.params[:token].to_s
      email = Base64.decode64(token)
      User.find_by(email: email)
    end
  end
end

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# app/graphql/mutations/add_item_mutation.rb

module Mutations
  class AddItemMutation < Mutations::BaseMutation
    argument :attributes, Types::ItemAttributes, required: true

    field :item, Types::ItemType, null: true
    field :errors, [String], null: false

    def resolve(attributes:)
      check_authentication!

      item = Item.new(attributes.merge(user: context[:current_user]))

      if item.save
        MartianLibrarySchema.subscriptions.trigger("itemAdded", {}, item)
        { item: item }
      else
        { errors: item.errors.full_messages }
      end
    end
  end
end

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# app/graphql/types/subscription_type.rb

module Types
  class SubscriptionType < GraphQL::Schema::Object
    field :item_added, Types::ItemType, null: false, description: "An item was added"
    field :item_updated, Types::ItemType, null: false, description: "Existing item was updated"

    def item_added; end
    def item_updated; end
  end
end

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# app/graphql/mutations/update_item_mutation.rb

module Mutations
  class UpdateItemMutation < Mutations::BaseMutation
    argument :id, ID, required: true
    argument :attributes, Types::ItemAttributes, required: true

    field :item, Types::ItemType, null: true
    field :errors, [String], null: false

    def resolve(id:, attributes:)
      check_authentication!

      item = Item.find(id)

      if item.update(attributes.to_h)
        MartianLibrarySchema.subscriptions.trigger("itemUpdated", {}, item)
        { item: item }
      else
        { errors: item.errors.full_messages }
      end
    end
  end
end