>GraphQL 既是一種用於 API 的查詢語言也是一個知足你數據查詢的運行時。GraphQL 對你的 API 中的數據提供了一套易於理解的完整描述,使得客戶端可以準確地得到它須要的數據,並且沒有任何冗餘,也讓 API 更容易地隨着時間推移而演進,還能用於構建強大的開發者工具。json
> ——出自 https://graphql.cn
上一篇博文中,咱們返回值是一個字符串,對於大多數狀況,咱們更多的是返回實體類的json格式。ide
using HotChocolate; using HotChocolate.Data; using HotChocolate.Execution; using HotChocolate.Types; using System; using System.Collections.Generic; namespace GraphQLBase002 { class Program { static void Main(string[] args) { FirstVersion.Run(); } } //實體類 public class Student { public int Id { get; set; } public string Name { get; set; } public int Age { get; set; } } #region FirstVersion public class FirstVersion { public static void Run() { var schema = SchemaBuilder.New() .AddQueryType<QueryType>() .Create(); var executor = schema.MakeExecutable(); //回爲返回是字符串,因此用定義的Resolver name來查詢 Console.WriteLine(executor.Execute("{ students }").ToJson()); } public class Query { public IList<Student> GetStudents() { return new List<Student>() { new Student { Id = 100, Name = "ABCD", Age=20 }, new Student { Id = 101, Name = "EFGH", Age=19 } }; } } public class QueryType : ObjectType<Query> { protected override void Configure(IObjectTypeDescriptor<Query> descriptor) { //定義了有students來請求GetStudents方法,返回的類型是StringType,因此在Resolver中會把實體轉成Json descriptor.Field<Query>(t => t.GetStudents()).Name("students").Type<NonNullType<StringType>>().Resolver(ctx => { var result = ctx.Parent<Query>().GetStudents(); return Newtonsoft.Json.JsonConvert.SerializeObject(result); }); } } } #endregion
爲了返回一個json,用Resolver來獲取GetStudents,並把實例親手轉成json返回,由於是字符串,因此這個Field的Type是StringType。工具
運行結果,看起來是個json,不,準確說是一個json格式的字符串,其實從咱們定義Resolver來講就很是清楚了;這並非咱們想要的。ui
#region SecondVersion public class SecondVersion { public static void Run() { var schema = SchemaBuilder.New() .AddQueryType<QueryType>() .Create(); var executor = schema.MakeExecutable(); Console.WriteLine(executor.Execute("{ student {id name} }").ToJson()); Console.WriteLine(executor.Execute("{ students {id name} }").ToJson()); } public class Query { public Student GetStudent() { return new Student { Id = 1, Name = "AAAAA", Age = 19 }; } public List<Student> GetStudents() { return new List<Student>{ new Student { Id = 100, Name = "ABCD", Age = 19 }, new Student { Id = 101, Name = "EFGH", Age = 20 } }; } } public class StudentType : ObjectType<Student> { protected override void Configure(IObjectTypeDescriptor<Student> descriptor) { } } public class QueryType : ObjectType<Query> { protected override void Configure(IObjectTypeDescriptor<Query> descriptor) { descriptor.Field(t => t.GetStudent()).Type<NonNullType<StudentType>>().Name("student"); descriptor.Field(t => t.GetStudents()).Type<ListType<NonNullType<StudentType>>>().Name("students"); } } } #endregion
此次咱們爲了避免再是json格式字符串,在代碼中定義了StudentType這個的類型,告訴系統Student不是一個簡單類型,但Student內的屬性,都是簡單類型,因此在Configure中沒有做任何處理(若是Student中有自定義複雜類型的屬性,還得進一步定義這個類型,並在Configure中處理),在QueryType中,處理了Query中的兩個方法的類型定義和重命名。spa
運行結果以下,對,這就是咱們要的結果;但總以爲爲了實現返回json,咱們的代價是否是有點大?code
#region ThreeVersion public class ThreeVersion { public static void Run() { var schema = SchemaBuilder.New() .AddProjections() .AddQueryType<Query>() .Create(); var executor = schema.MakeExecutable(); Console.WriteLine(executor.Execute("{ student{id name age} }").ToJson()); Console.WriteLine(executor.Execute("{ students{id name age} }").ToJson()); } public class Query { [UseProjection] public Student GetStudent() { return new Student { Id = 1, Name = "AAAAA", Age = 19 }; } [UseProjection] public List<Student> GetStudents() { return new List<Student>{ new Student { Id = 100, Name = "ABCD", Age = 19 }, new Student { Id = 101, Name = "EFGH", Age = 20 } }; } } } #endregion
這一版咱們借雞下蛋,用UseProjection來替代了咱們定義的類型,連QueryType也消失了,這樣的代碼纔是咱們想要的,讓咱們更關注業務的邏輯,而不是關注爲了GraphQL,而作不少技術配合工做;其實咱們從第二版看定義的類型StudentType,QueryType,也知道這些類型是很是規律性的,是能夠經過代碼手段替代的,那就是UseProjection。blog
運行結果與版本二同樣。ip