确保字符串是带流的十六进制值 [英] Ensure string is a hex value with flow

问题描述

我想确保我得到的值是一个十六进制字符串.目前我说

I would like to ensure that a value I get is a hex string. Currently I say

type Color = string;
function foo(color: Color){}

但是我想说

type Color = '#' + stringOfLength-3-6-8;
function foo(color: Color){}

有没有一种方法可以表达这种约束?

Is there a way to express constraints like this in flow?

推荐答案

不，这不是类型系统可以表达的.您可以创建一个由字面量的并集(例如type Foo = 'foo' | 'bar' | ...)组成的类型，但是除非您可以枚举每个可能的字符串，否则您将无法完成所要查询的内容.

No, this is not something that the type system can express. You can create a type which is a union of literals (e.g. type Foo = 'foo' | 'bar' | ...) but unless you can enumerate every possible string, you can't accomplish what you're asking.

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