Flow中的非null和非undefined类型

Question

Flow定义了所谓的"Maybe types"。即?string与string | null | void类似（void是一种值undefined）。

是否存在类似于null和undefined的任何值的常规类型？如果$Diff<$Diff<any, null>, void>运算符，基本上类似于$Diff能够在非对象类型上操作。

Answer 1

没有一些＆＃34;魔法＆＃34;为此类型，但这样的事情应该有效：string | number | boolean | {} | []

Answer 2

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

  

$NonMaybeType<T>将类型T转换为非也许类型。换句话说，$NonMaybeType<T>的值是T的值，除了null和undefined之外。

// @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