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GraphQLのFieldを条件に応じて返却する方法

2024/04/22に公開

GraphQL

Rails

GraphQL Ruby

tech

方法

条件に応じて返却したいFieldと同じ名前のメソッド(=custom method)を定義する。
- 参考
  - https://graphql-ruby.org/fields/introduction.html
    
    by default the custom method name must match the field name

実装/動作確認

使用するType

book_type.rb

# frozen_string_literal: true
  
module Types
  class BookType < Types::BaseObject
    field :id, ID, null: false
    field :title, String, null: false
    field :user, UserType, null: false
  end
end

user_type.rb

Custom Methodを使う場合

  # frozen_string_literal: true

  module Types
    class UserType < Types::BaseObject
      field :id, ID, null: false
      field :name, String, null: false
      field :books, [BookType], null: false

      # custom method
      def books
        return [] if object.id == 6
        object.books
      end
    end
  end

実行結果

  # Request
  {
    user(id:6) {
      id
      name
      books {
        id
        title
      }
    }
  }
  
  # Response
  {
    "data": {
      "user": {
        "id": "6",
        "name": "user6",
        "books": [] # custom methodにより[]が返却された
      }
    }
  }
  
  # Request
  {
    user(id:7) {
      id
      name
      books {
        id
        title
      }
    }
  }
  
  # Response
  {
    "data": {
      "user": {
        "id": "7",
        "name": "user7",
        "books": [
          {
            "id": "4",
            "title": "BarBook"
          }
        ]
      }
    }
  }

Custom Methodを使わない場合

  # frozen_string_literal: true
    
  module Types
      class UserType < Types::BaseObject
      field :id, ID, null: false
      field :name, String, null: false
      field :books, [BookType], null: false
        
          # custom method
          # def books
          #   return [] if object.id == 6
          #   object.books
          # end
      end
  end

実行結果

# Request
{
  user(id:6) {
    id
    name
    books {
      id
      title
    }
  }
}

# Response
{
  "data": {
    "user": {
      "id": "6",
      "name": "user6",
      "books": [
        # custom methodをコメントアウトしたのでBooksが返却された
        {
          "id": "3",
          "title": "FooBook"
        }
      ]
    }
  }
}

# Request
{
  user(id:7) {
    id
    name
    books {
      id
      title
    }
  }
}

# Response
{
  "data": {
    "user": {
      "id": "7",
      "name": "user7",
      "books": [
        {
          "id": "4",
          "title": "BarBook"
        }
      ]
    }
  }
}

方法

実装/動作確認

Discussion