TypeScript 泛型和函数参数

Question

我正在努力改进 Rosie 的定义，它目前非常依赖 any 并且在安全方面没有提供太多。我现在有点卡住了，需要一些建议。

我正在尝试编写一个表达以下内容的签名:

// this is invalid, but something like this is the goal
interface IFactory<T = any> {
  attr<K extends keyof T, D extends keyof T>(name: K, dependencies: D[], generatorFunction: (value1?: D[0], value2?: D[1], value3?: D[2]), value4?: D[3] => T[K]): IFactory<T>;
}

第二个参数给出了一个键数组。这些值以提供的相同顺序作为参数传递给函数。我想避免不必要的类型转换，所以我们应该得到这个:

Factory.define<Person>('Person').attr('fullName', ['firstName', 'lastName', 'age'], (firstName, lastName, age) => {
   // it knows that firstName is a string, lastName is a string, age is a number

  if (age > 10) { 
    // this will error
    return age; 
  }

  return `${firstName} ${lastName};     
});

我能得到的最接近的是:

attr<K extends keyof T, D extends keyof T>(name: K, dependencies: D[], generatorFunction: (value1: T[D], value2: T[D], value3: T[D], value4: T[D]) => T[K]): IFactory<T>;

这将键入最多 4 个依赖值，但调用它需要显式转换并且它不会以正确的顺序设置类型:

// it knows that each of the three arguments are string | number
existingDefinition.attr('fullName', ['firstName', 'lastName', 'age'], (firstName: string, lastName: string, age: number) => `${firstName} ${lastName}`);

这使我可以在不破坏依赖项的情况下更改依赖项的顺序，这不好。如果我提供的参数多于依赖值，它也不会给出错误。我想找到一种方法来表达“generatorFunction 对 dependencies 中的每个元素都有一个参数，类型为 T[DependencyName]”。

我希望这是有道理的。感谢任何人可以提供的任何帮助。

Answer 1

您需要为每个元数(签名)进行重载。例如，看看如何 Reselect做事

/* one selector */
export function createSelector<S, R1, T>(
  selector: Selector<S, R1>,
  combiner: (res: R1) => T,
): OutputSelector<S, T, (res: R1) => T>;
export function createSelector<S, P, R1, T>(
  selector: ParametricSelector<S, P, R1>,
  combiner: (res: R1) => T,
): OutputParametricSelector<S, P, T, (res: R1) => T>;

/* two selectors */
export function createSelector<S, R1, R2, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  combiner: (res1: R1, res2: R2) => T,
): OutputSelector<S, T, (res1: R1, res2: R2) => T>;
export function createSelector<S, P, R1, R2, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  combiner: (res1: R1, res2: R2) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2) => T>;

/* three selectors */
export function createSelector<S, R1, R2, R3, T>(
  selector1: Selector<S, R1>,
  selector2: Selector<S, R2>,
  selector3: Selector<S, R3>,
  combiner: (res1: R1, res2: R2, res3: R3) => T,
): OutputSelector<S, T, (res1: R1, res2: R2, res3: R3) => T>;
export function createSelector<S, P, R1, R2, R3, T>(
  selector1: ParametricSelector<S, P, R1>,
  selector2: ParametricSelector<S, P, R2>,
  selector3: ParametricSelector<S, P, R3>,
  combiner: (res1: R1, res2: R2, res3: R3) => T,
): OutputParametricSelector<S, P, T, (res1: R1, res2: R2, res3: R3) => T>;

// etc...

对每个参数进行重载，直到达到合理的数量(您期望多少？4？8？)，然后仅使用非限制性泛型并让用户输入。如果您的参数超过 8 个，应该打字不方便。