如何使用io-ts验证数组长度? [英] How to validate array length with io-ts?

问题描述

我正在进行 io-ts 验证，我想验证列表长度(必须在最小和最大之间).我想知道是否有一种方法可以实现此行为，因为在运行时可以很方便地进行API端点验证.

I am working on an io-ts validation where I would like to validate the list length (it has to be between min and max). I am wondering if there's a way to achieve this behavior since it could come quite handy at runtime for API endpoint validation.

到目前为止，我是

interface IMinMaxArray {
  readonly minMaxArray: unique symbol // use `unique symbol` here to ensure uniqueness across modules / packages
}

const minMaxArray = (min: number, max: number) => t.brand(
  t.array,
  (n: Array): n is t.Branded<Array, IMinMaxArray> => min < n.length && n.length < max,
  'minMaxArray'
);

上面的代码不起作用，它需要 Array -s的参数，并且也不接受 t.array .我该如何以通用方式进行这项工作?

The code above does not work, it requires an argument for the Array-s and t.array is also not accepted. How could I make this work in a generic way?

推荐答案

您的定义缺少数组的类型和编解码器.您可以对接口定义进行一些修改，并使用编解码器扩展品牌类型，从而完成这项工作:

Your definition is missing the typing and the codec for the array. You could make this work with a few modifications on the interface definition and extending the branded type with a codec:

interface IMinMaxArray<T> extends Array<T> {
  readonly minMaxArray: unique symbol
}

const minMaxArray = <C extends t.Mixed>(min: number, max: number, a: C) => t.brand(
  t.array(a),
  (n: Array<C>): n is t.Branded<Array<C>, IMinMaxArray<C>> => min < n.length && n.length < max,
  'minMaxArray'
);

现在您可以创建类似的定义

Now you can create a definition like

minMaxArray(3,5, t.number)

如果您希望定义更加通用和可组合，则可以编写一个接受谓词的通用品牌类型:

If you want the definition to be more generic and composable, you could write a generic branded type that accepts a predicate:

interface RestrictedArray<T> extends Array<T> {
  readonly restrictedArray: unique symbol
}

const restrictedArray = <C>(predicate: Refinement<C[], ArrayOfLength<C>>) => <C extends t.Mixed>(a: C) => t.brand(
  t.array(a), // a codec representing the type to be refined
  (n): n is t.Branded<C[], RestrictedArray<C>> => predicate(n), // a custom type guard using the build-in helper `Branded`
  'restrictedArray' // the name must match the readonly field in the brand
)

interface IRestrictedArrayPredicate<C extends t.Mixed> {
  (array: C[]): array is ArrayOfLength<C>
}

现在您可以定义限制.分别定义min和max可能是一个好主意，因为它们也可以单独使用:

Now you can define your restrictions. It's probably a good idea to define min and max separately, since they can be useful on their own too:

const minArray = <C extends t.Mixed>(min: number) 
  => restrictedArray(<IRestrictedArrayPredicate<C>>((array) => array.length >= min));
const maxArray = <C extends t.Mixed>(max: number)
  => restrictedArray(<IRestrictedArrayPredicate<C>>((array) => array.length <= max));

将这两者结合起来可以定义minMaxArray:

And combining these two you can define minMaxArray:

export const minMaxArray = <C extends t.Mixed>(min: number, max: number, a: C) => t.intersection([minArray(min)(a), maxArray(max)(a)])

希望这会有所帮助.

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