flow-static-maybe:代表可选值的不透明类型别名

流动静态也许 一个简单的作为Flow 的替代方案。 opaque type Maybe < A> = null | A 使用不透明类型的好处 不透明的类型别名是不允许在定义它们的文件之外访问其基础类型的类型别名。 这样可以确保只能使用提供的函数来创建和操作Maybe类型的值。 // @flow import type { Maybe } from 'flow-static-maybe' import { just , nothing } from 'flow-static-maybe' const a : Maybe < string> = null // null This type is incompatible with Maybe const b: Maybe < string> = 'foo' // string This type is