Flow 中的非空和非未定义类型

Question

流量定义所谓"Maybe types"。 IE。 ?string类似于string | null | void（void是一种值undefined）。

除了null和undefined之外，是否有类似通用类型的东西可以是任何值？基本上像$Diff<$Diff<any, null>, void>如果$Diff 运算符能够对非对象类型进行操作。

Answer 1

这里没有一些 "magic" 类型，但像这样的东西应该可以工作：string | number | boolean | {} | []

Answer 2

可以使用 NonMaybeType Flow 实用程序类型：参见 $NonMaybeType

$NonMaybeType<T> converts a type T to a non-maybe type. In other words, the values of $NonMaybeType<T> are the values of T except for null and undefined.

// @flow
type MaybeName = ?string;
type Name = $NonMaybeType<MaybeName>;

('Gabriel': MaybeName); // Ok
(null: MaybeName); // Ok
('Gabriel': Name); // Ok
(null: Name); // Error! null can't be annotated as Name because Name is not a maybe type

Flow 中的非空和非未定义类型

Non-null and non-undefined type in Flow

non-nullable

flowtype