TypeScript:从某种类型创建联合类型的字符串

Question

我有一个 IconName 类型，如下所示:

type IconName = 'cars' | 'mars' | 'truck' | 'warning'

然后我想创建另一种 VehicleIconName 类型，其中包含与车辆相关的所有图标名称:

type VehicleIconName = 'cars' | 'truck'

但是我如何告诉 TypeScript VehicleIconName 中的每个字符串也必须是 IconName 类型？

所以我不能这样写:

type VehicleIconName = 'cars' | 'truck' | 'invalidIconName'

Answer 1

你可以添加一个助手类型:

type Subset<Parent, Sub extends Parent> = Extract<Parent, Sub>;

type IconName = 'cars' | 'mars' | 'truck' | 'warning'

type VehicleIconName = Subset<IconName, 'cars' | 'truck' | 'invalidName'>

最后一行错误:

Type '"cars" | "truck" | "invalidName"' does not satisfy the constraint 'IconName'.
  Type '"invalidName"' is not assignable to type 'IconName'.ts(2344)