打字稿:如何将项目添加到元组? [英] Typescript: How to add an item to a tuple?

问题描述

为什么这会产生错误其余元素类型必须是数组类型."?

Why this produces an error "A rest element type must be an array type."?

type QWE<T extends [number, string]> = [boolean, ...T]
                                                 ^^^^ the error is here

推荐答案

在 3.0 之前，我们无法将元组或泛型类型参数传播给函数，因此必须实现这一点.类似地，元组中的其余部分目前仅支持数组，没有人实现将其他元组传播到给定元组的其余部分的能力，我猜想实现它需要大量的努力和复杂性.

Before 3.0 we could not spread tuples or generic type arguments to a function and this had to be implemented. Similarly, rest in tuples currently only support arrays, nobody implemented the ability to spread other tuples into the rest of a given tuple, and I'm guessing implementing it would require significant effort and complexity.

要在另一个已知元组的末尾添加一个元组，我们可以使用将元组扩展为一个函数，然后将参数类型提取为元组的能力.

To add a tuple at the end of another known tuple we can use the ability to spread a tuple tu a function and then extract the argument types as a tuple.

type ArgumentTypes<T extends (...a: any) => any> =
    T extends (...a: infer A) => any ? A : never;
type QWE<T extends [number, string]> = 
    ArgumentTypes<(a: boolean, ...r: T) => void>

type R = QWE<[number, string]>

在开始时添加元组更成问题，我相信有一些非常不推荐的 hacks 可以使用递归类型别名来实现这一点.您还可以定义多个条件以支持一个元组中的多个元素，但如果可能，我会避免使用它

Adding the tuple at the start is more problematic, I believe there are some very unrecommended hacks that can achieve this using recursive type aliases. You can also define multiple conditions to support up to a number of elements in a tuple, but I would avoid it if possible

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