arrays - [首先，...休息] : A spread argument must either have a tuple type or be passed to a rest parameter. ts(2556)

Question

设置

class X {
    constructor(first: string, ...rest: string[]) { }
}

new X(...["foo", "bar"])

产生错误

A spread argument must either have a tuple type or be passed to a rest parameter.ts(2556)

这正在工作:

new X("foo", ...["bar"])

但这不是很方便。

如果我使用

class X {
    constructor(...all: string[]) { }
}

相反，它工作正常，所以它一定与我分成 first 和 rest 有关。但是有没有办法让这个工作与分割参数一起工作？

Answer 1

["foo", "bar"] 的类型是 string[]。如果您无法使用 as const 控制 this 的类型，因为您在其他地方获得了它，则可以验证并缩小类型，例如:

const input:string[] = ["foo", "bar"];

if (!input.length<1) {
  throw new Error('Input must at least have 1 element');
}
const tuple: [string, ...string[]] = [input[0], ...input.slice(1)];
}

如果作业感觉很傻，我觉得这样更优雅:

const input:string[] = ["foo", "bar"];

function assertAtLeast1Element(input: string[]): asserts input is [string, ...string[]] {
  if (input.length < 1) throw new Error('Input must at least have 1 element');
}

assertAtLeast1Element(input);

class X {
    constructor(first: string, ...rest: string[]) { }
}

new X(...input);