使用泛型输入 Api 配置

Question

我正在尝试强制键入后端处理，但在泛型如何与 ...args 交互时遇到问题。

以下是带有声明和 2 个用例的代码示例。案例之间的唯一区别是在第一种情况下明确设置了配置类型。

问题

• 在第一种情况下 - 配置输入良好，但实例输入缺乏。
• 在第二种情况下 - 配置输入缺少，但实例输入良好。

理想情况下，我希望 良好 输入配置和服务。

我尝试了Parameters<typeof someFunction>，它可以正常工作，只有泛型有时会失败。

检查TS playground，以便您了解它是如何工作的（您可以将鼠标悬停以检查类型等）。 TS 版本为4.1.3。

提前感谢您的帮助。

/************** DECLARATION ******************/

interface EndpointConfig {
  in: (...args: any) => void
  out: (value: 'correct') => void
}
type EndpointConfigs = Record<string, EndpointConfig>

class ApiService<ENDPOINT_CONFIGS extends EndpointConfigs> {
  constructor( public endpointConfigs: ENDPOINT_CONFIGS ) {}

  endpoint <ENDPOINT extends keyof ENDPOINT_CONFIGS>(endpoint: ENDPOINT): ApiEndpoint<ENDPOINT_CONFIGS, ENDPOINT> {
    return new ApiEndpoint( endpoint )
  }
}

class ApiEndpoint<ENDPOINT_CONFIGS extends EndpointConfigs, ENDPOINT extends keyof ENDPOINT_CONFIGS> {
  constructor( public endpoint: ENDPOINT ) {}

  async run (...args: Parameters<ENDPOINT_CONFIGS[ENDPOINT]['in']>): Promise<any> {}
}

/************** CASE 1 *******************/

const endpointConfigs1: EndpointConfigs = {
  testEndpoint: {
    in: (value: 'correct') => {},
    out: (value) => { value++ } // <- Complains here. Which is correct.
  }
};

const apiServiceInstance1 = new ApiService(endpointConfigs1)
const testEndpoint1 = apiServiceInstance1.endpoint('testEndpoint')
testEndpoint1.run('wrong') // <- Doesn't complain here. Which is NOT what we want.


/************** CASE 2 *******************/

const endpointConfigs2 = {
  testEndpoint: {
    in: (value: 'correct') => 'wrong',
    out: (value) => { value++ } // <- value is considered `any` here. Which is NOT what we want.
  }
};

const apiServiceInstance2 = new ApiService(endpointConfigs2)
const testEndpoint2 = apiServiceInstance2.endpoint('testEndpoint')
testEndpoint2.run('wrong') // <- Complains here, which is what we want.

Answer 1

可以通过一个小技巧让 TS 推断出某些类型。这是一个可以在各种情况下应用的最小工作示例：

const trick = <K extends string>(k: K) => k
// has type "test"
const test = trick("test")

让我们看看我们如何在您的上下文中应用它 (Playground link)：

interface EndpointConfig<Args extends any[]> {
  in: (...args: Args) => void
  out: (value: 'correct') => void
}


type ConfigDeclaration<P extends Record<string, any[]>> = {
    [k in keyof P]: EndpointConfig<P[k]>
}


type InType<Cfg extends EndpointConfig<any>> =
  Cfg extends EndpointConfig<infer Args>
    ? Args
    : never


// This is a trick to infer the correct type.
// I think the JIT compiler should take care of the runtime overhead
const trick = <P extends Record<string, any[]>>(
  declaration: ConfigDeclaration<P>
  ): ConfigDeclaration<P> =>
    declaration


// Here, we apply the trick
const endpointConfigs = trick({
  testEndpoint: {
    in: (value: "correct") => 'wrong',
    // The type of `value` is inferred as intended.
    out: value => {  } 
  }
})


// The type is as intended
type Test = {
  [k in keyof typeof endpointConfigs]: InType<typeof endpointConfigs[k]>
}


class ApiService<D extends ConfigDeclaration<any>> {
  constructor( public endpointConfigs: D ) {}

  endpoint <ENDPOINT extends keyof D>(endpoint: ENDPOINT): ApiEndpoint<D, ENDPOINT> {
    return new ApiEndpoint( endpoint )
  }
}


class ApiEndpoint<D extends ConfigDeclaration<any>, ENDPOINT extends keyof D> {
  constructor( public endpoint: ENDPOINT ) {}

  async run (...args: InType<D[ENDPOINT]>): Promise<any> {}
}


const apiServiceInstance2 = new ApiService(endpointConfigs)
const testEndpoint2 = apiServiceInstance2.endpoint('testEndpoint')


testEndpoint2.run('wrong') // <- Complains here, which is what we want.
testEndpoint2.run("correct")