使用 generics 獲取嵌套類型

Question

我有一個 object 服務，每個都有嵌套請求。 我正在嘗試創建一個 function 來獲取特定請求，並希望 output 上的類型正確。

考慮以下代碼：

enum Service {
  Foo = 'foo',
  Bar = 'bar'
}

const services = {
  [Service.Foo]: {
    v1: {
      getGreeting: (id: string) => 'hello',
    },
  },
  [Service.Bar]: {
    v2: {
      getInsult: () => 'idiot',
    },
  },
};

function createRequest<T extends Service>(
  serviceName: T,
  version: string,
  endpoint: string,
) {
  const service = services[serviceName] as typeof services[T];
  return service[version][endpoint];
}

const request = createRequest(Service.Foo, 'v1', 'getGreeting');

我快到了，但request的類型是any 。 function 已經通過 generics 知道服務的類型，但是我如何通過 go 獲得額外的英里來獲得返回的嵌套屬性的類型？

Answer 1

讓我們為服務數據結構創建一個接口：

type ServiceType = Record<Service, Record<string, Record<string, (...args: any[]) => any>>>;

現在，為了推斷所有 arguments 並驗證它們，我們需要將此 function 設為pure 。 TS 更喜歡pure函數。 我們應該創建一個 function 它將返回另一個 function （ curry它）

const withService = <
  ServiceObj extends ServiceType
>(services: ServiceObj) =>
  <
    Name extends keyof ServiceObj,
    Version extends keyof ServiceObj[Name],
    Endpoint extends keyof ServiceObj[Name][Version]
  >(
    serviceName: Name,
    version: Version,
    endpoint: Endpoint,
  ) => services[serviceName][version][endpoint];

現在我們可以測試它：

const request = withService({
  [Service.Foo]: {
    v1: {
      getGreeting: (id: string) => 'hello',
    },
  },
  [Service.Bar]: {
    v2: {
      getInsult: () => 'idiot',
    },
  },
})

// (id: string) => string
const createRquest = request(Service.Foo, 'v1', 'getGreeting')

// () => string
const createRquest2 = request(Service.Bar, 'v2', 'getInsult')

const createRquest3 = request(Service.Bar, 'v22', 'getInsult') // expected error

操場

您可能已經注意到keyof ServiceObj[Name][Version]反映了 function 主體邏輯

如果你對 function 參數推理感興趣，可以查看我的相關文章

---

在這里，您有一個帶有類的版本：

enum Service {
  Foo = 'foo',
  Bar = 'bar'
}

interface Base {
  [prop: `v${number}`]: Record<string, Fn>
}

class Foo {
  v1 = {
    getGreeting: (id: string) => 2,
  }
}

class Bar {
  v2 = {
    getInsult: () => 'idiot',
  }
}

type WithoutIndex = keyof Bar
const services = {
  [Service.Foo]: Foo,
  [Service.Bar]: Bar,
}

type AnyClass = new (...args: any[]) => Base
type Fn = (...args: any[]) => any


function withService<
  ServiceObj extends Record<Service, new (...args: any[]) => any>,
  >(services: ServiceObj):
  <Name extends Service,
    Version extends keyof InstanceType<ServiceObj[Name]>,
    Endpoint extends keyof InstanceType<ServiceObj[Name]>[Version]
    >(
    serviceName: Name,
    version: Version,
    endpoint: Endpoint,
    v?: keyof InstanceType<ServiceObj[Name]>
  ) => InstanceType<ServiceObj[Name]>[Version][Endpoint]
function withService<
  ServiceObj extends Record<Service, AnyClass>,
  >(services: ServiceObj) {
  return <Name extends Service,
    Version extends keyof Base,
    Endpoint extends keyof Base[Version]
  >(
    serviceName: Name,
    version: Version,
    endpoint: Endpoint,
  ) => {
    const api = new services[serviceName]();
    return api[version][endpoint];
  }
};


const request = withService({
  [Service.Foo]: Foo,
  [Service.Bar]: Bar,
})

// (id: string) => number
const createRquest = request(Service.Foo, 'v1', 'getGreeting')

// () => string
const createRquest2 = request(Service.Bar, 'v2', 'getInsult')

const createRquest3 = request(Service.Bar, 'v22', 'getInsult') // expected error

操場