Typescript 使用 keyof 时，索引签名参数类型必须为 'string' 或 'number'

Question

使用 Typescript，我尝试编写一个函数，该函数接受通用对象和验证规则的键值映射以应用于每个属性。当使用 keyof 属性来验证“validators”对象中传递的 key 是否在 TObject 泛型中时，我得到 An indexsignatureparametertypemustbe'string'or'number'。后来，当尝试访问验证器中的值时，我得到No indexsignature with a type 'string' was found on type '{}'。

function isValid<TObject>(
  o: TObject,
  validators: {
    [key: keyof TObject]: (o: TObject) => boolean;
  }
) {
  for (const validator in validators) {
    if (!validators[validator](o)) {
      return false;
    }
  }

  return true;
}

type Todo = {
  text: string;
  details: string;
  completed: boolean;
};

console.log(
  isValid<Todo>(
    {
      text: "mow yard",
      details: "needs to be completed asap",
      completed: false
    },
    {
      text: (o: Todo) => o.text.length > 0,
      completed: (o: Todo) => !!o.completed
    }
  )
);

Answer 1

您应该使用关键字 in 而不是 :，因为 : 用于索引类型(字符串、数字、符号)

function isValid<TObject>(
  o: TObject,
  validators: {
    [key in keyof TObject]: (o: TObject) => boolean;
  }
) {
  for (const validator in validators) {
    if (!validators[validator](o)) {
      return false;
    }
  }

  return true;
}

如果 key 是可选的，请使用?:

  validators: {
    [key in keyof TObject]?: (o: TObject) => boolean;
  }