使用 ObjectType 字段扩展类型

Question

我是 HotChocolate 和 GraphQL 的新手，我在类型扩展方面遇到了一些困难。

是否可以使用ObjectType 字段扩展类型？我在StringType 的文档中只找到了一个示例：

protected override void Configure(IObjectTypeDescriptor descriptor)
{
    descriptor.Name("Person");
    descriptor.Field("address")
        .Type<StringType>()
        .Resolver("Address");
}

我尝试做类似的事情，但我有这个例外HotChocolate.SchemaException: Unable to resolve type reference Output: ObjectType。

protected override void Configure(IObjectTypeDescriptor descriptor)
{
    descriptor.Name("Person");
    descriptor.Field("address")
        .Type<ObjectType>()
        .Resolver(ctx => new ObjectType(d => d.Field("street").Type<StringType>().Resolver("Street")));
}

在我的情况下，您能否建议任何使用 ObjectType 字段扩展类型的方法？还是直接回答有没有可能？

谢谢！

Answer 1

假设，您的类 Book 包含一些 JSON 字段“数据”。 “数据”的结构可以在重新启动之间更改，但在任何启动之前都是已知的（即您在启动时知道属性名称及其类型）。 以下代码解决了这种情况：

using System.Linq;
using HotChocolate.Resolvers;
using HotChocolate.Types;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Newtonsoft.Json.Linq;

namespace Ademchenko.GraphQLWorkshop
{
    public class Book
    {
        public int Id { get; set; }

        public JObject Data { get; set; }
    }

    public interface IBookService { IQueryable<Book> GetAll(); }

    public class InMemoryBookService : IBookService
    {
        private readonly Book[] _staticBooks = {
            new Book {Id = 11, Data = JObject.FromObject(new {Title = "FooBook", AuthorId = 1, Price = 10.2m})},
            new Book {Id = 22, Data = JObject.FromObject(new {  Title = "BarBook", AuthorId = 2, Price = 20.2m})}
        };

        public IQueryable<Book> GetAll() => _staticBooks.AsQueryable();
    }

    public class Query
    {
        public IQueryable<Book> GetBooks(IResolverContext ctx) => ctx.Service<IBookService>().GetAll();
    }

    public class BookType : ObjectType<Book>
    {
        protected override void Configure(IObjectTypeDescriptor<Book> descriptor)
        {
            descriptor.Field(d => d.Data).Type<DataType>();
        }
    }

    public class DataType : ObjectType
    {
        protected override void Configure(IObjectTypeDescriptor descriptor)
        {
            descriptor.Field("title").Type<StringType>().Resolve((ctx, ct) => (string)ctx.Parent<JObject>()["Title"]);
            descriptor.Field("authorId").Type<IntType>().Resolve((ctx, ct) => (int)ctx.Parent<JObject>()["AuthorId"]);
            descriptor.Field("price").Type<DecimalType>().Resolve((ctx, ct) => (decimal)ctx.Parent<JObject>()["AuthorId"]);
        }
    }

    public class Startup
    {
        public IConfiguration Configuration { get; }

        public Startup(IConfiguration configuration) => Configuration = configuration;

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();

            services.AddSingleton<IBookService, InMemoryBookService>();

            services.AddGraphQLServer()
                .AddQueryType<Query>()
                .AddType<BookType>();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env) => app.UseRouting().UseEndpoints(endpoints => endpoints.MapGraphQL());
    }
}

向服务器发出请求：

{
  books
  {
    id,
    data
    {
      title
      authorId
      price
    }
  } 
}

你会得到以下响应：

{
  "data": {
    "books": [
      {
        "id": 11,
        "data": {
          "title": "FooBook",
          "authorId": 1,
          "price": 1
        }
      },
      {
        "id": 22,
        "data": {
          "title": "BarBook",
          "authorId": 2,
          "price": 2
        }
      }
    ]
  }
}