Ruby on rails 轨道&x2B；GraphQL-未知属性'；字符'；游戏

我对rails和graphql都是新手。我试图实现一些简单的API，包含3种类型的对象、游戏、角色和引号。每个游戏可以有多个角色。以下是我写的类型和突变。（问题在于游戏和角色，所以我只粘贴它们。）

游戏类型：

module Types
  class GameType < Types::BaseObject
    field :id, ID, null: false
    field :name, String, null: false

    field :characters, [Types::CharacterType], null: true do
      #pagination, and cap number of characters retrieved to 20
      argument :first, Integer, default_value: 20, required: false, prepare: ->(limit, ctx) {[limit, 20].min}
      argument :offset, Integer, default_value: 0, required: false
    end

    field :quotes, [Types::QuoteType], null: true do
      #pagination, and cap number of quotes retrieved to 20
      argument :first, Integer, default_value: 20, required: false, prepare: ->(limit, ctx) {[limit, 20].min}
      argument :offset, Integer, default_value: 0, required: false
    end

    field :character_count, Integer, null: true
    field :quote_count, Integer, null: true

    def characters(first:, offset:)
      object.characters.first(first).offset(offset)
    end

    def quotes(first:, offset:)
      object.quotes.first(first).offset(offset)
    end

    def character_count
      object.characters.count
    end

    def quote_count
      object.quotes.count
    end
  end
end

CreateGame工作正常，但CreateCharacter给了我此错误（CreateCharacter中已标记行）：

未定义的方法“字符”#
/var/lib/gems/2.5.0/gems/activemodel-6.0.2.2/lib/active\u model/attribute\u methods.rb:431:in'method\u missing'
/home/krypt/myStuff/projects/gameq/gameq_api/app/graphql/mutations/create_character.rb:19:in'resolve'

---

我该如何解决这个问题？谢谢

在角色模型中，您与游戏有关联：

class Character < ApplicationRecord
  belongs_to :game
end

这将生成您缺少的

Game#characters

方法。Rails魔术在这里再次发挥作用。因为您使用了名称

characters

，它将知道如何查找所有

Character

记录，这些记录具有指向游戏的

游戏id

。它如何知道使用

游戏id

作为外键？使用类的名称-

类游戏

class Mutations::CreateGame < Mutations::BaseMutation
  argument :name, String, required: true

  field :game, Types::GameType, null: false
  field :errors, [String], null: false

  def resolve(name:)
    game = Game.new(name: name)
    if game.save
      # Successful creation, return the created object with no errors
      {
        game: game,
        errors: [],
      }
    else
      # Failed save, return the errors to the client
      {
        game: nil,
        errors: game.errors.full_messages
      }
    end
  end
end

class Mutations::CreateCharacter < Mutations::BaseMutation
  argument :name, String, required: true
  argument :gameId, Integer, required: true

  field :character, Types::CharacterType, null: false
  field :errors, [String], null: false

  def resolve(name:, gameId:)
    game = Game.find(gameId)

    if game.nil?
        return {
                    character: nil,
                    errors: game.errors.full_messages,
        }
    end

    character = Character.new(name: name, game: game)
        game = game.update(characters: game.characters + [character]) 
        ^^^^^^ error on this line 
    if character.save
      # Successful creation, return the created object with no errors
      {
        character: character,
        errors: [],
      }
    else
      # Failed save, return the errors to the client
      {
        character: nil,
        errors: character.errors.full_messages + game.errors.full_messages
      }
    end
  end
end

class Game < ApplicationRecord
end

class Character < ApplicationRecord
  belongs_to :game
end

ActiveRecord::Schema.define(version: 2020_04_30_071223) do

  create_table "characters", force: :cascade do |t|
    t.integer "game_id", null: false
    t.string "name"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["game_id"], name: "index_characters_on_game_id"
  end

  create_table "games", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
  end

  create_table "quotes", force: :cascade do |t|
    t.integer "game_id", null: false
    t.integer "character_id", null: false
    t.string "text"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
    t.index ["character_id"], name: "index_quotes_on_character_id"
    t.index ["game_id"], name: "index_quotes_on_game_id"
  end

  add_foreign_key "characters", "games"
  add_foreign_key "quotes", "characters"
  add_foreign_key "quotes", "games"
end

undefined method `characters' for #<Game:0x00007fdf4c207c30>
/var/lib/gems/2.5.0/gems/activemodel-6.0.2.2/lib/active_model/attribute_methods.rb:431:in `method_missing'
/home/krypt/myStuff/projects/gameq/gameq_api/app/graphql/mutations/create_character.rb:19:in `resolve'

class Character < ApplicationRecord
  belongs_to :game
end

class Game < ApplicationRecord
  has_many :characters
end