Question

我有一个对象

const modalTypes = {
  newPizza: 'NEW_PIZZA',
  newCola: 'NEW_COLA',
  newCustom: 'NEW_CUSTOM,
}

然后我有一个动作创建者，该动作创建者执行的操作是modalTypes'值之一。

const showModal = (modalType: ModalType, body: BodyType) => {
  // do something...
}

// e.g.
showModal('NEW_PIZZA', ...)

如何使ModalType成为NEW_PIZZA | NEW_COLA | NEW_CUSTOM？

类似的东西，只是值。

const Foo = { a: 'FOO', b: 'BAR', c: 'BAZ' };
type Abc = keyof typeof Foo

Abc = 'a' | 'b' | 'c'
// Desired = 'FOO' | 'BAR' | 'BAZ'

Answer 1

就像@ExplosionPills所说的那样，没有额外的注释，值的类型是通用的，但是如果您可以添加注释，则可以：

const modalTypes = {
  newPizza: 'NEW_PIZZA' as 'NEW_PIZZA',
  newCola: 'NEW_COLA' as 'NEW_COLA',
  newCustom: 'NEW_CUSTOM' as 'NEW_CUSTOM',
}

type ModalType = typeof modalTypes[keyof typeof modalTypes]

Answer 2

您可以使用npm install typescript@next断言在3.4中进行操作而无需额外的断言（尚未发布，请使用as const进行尝试，请参见PR。

const modalTypes = {
  newPizza: 'NEW_PIZZA',
  newCola: 'NEW_COLA',
  newCustom: 'NEW_CUSTOM',
} as const

type ModalType = typeof modalTypes[keyof typeof modalTypes]

在3.4以下，我仍然不会走显式的断言路线，我宁愿使用一个辅助函数来推断正确的类型，它可以是IIFE：

const modalTypes = (<V extends string, T extends Record<string, V>>(o:T) => o)({
  newPizza: 'NEW_PIZZA',
  newCola: 'NEW_COLA',
  newCustom: 'NEW_CUSTOM',
})

type ModalType = typeof modalTypes[keyof typeof modalTypes]

Answer 3

如果ModalType是字符串常量的集合，则需要使用Enum代替这样的对象：

enum ModalType {
    newPizza = "NEW_PIZZA",
    newCola = "NEW_COLA",
    newCustom = "NEW_CUSTOM",
}
const showModal = (modalType: ModalType[keyof ModalType]) => {
    // do something...
};
showModal("NEW_PIZZA");

创建ENUM（-like）类型的对象值

3 个答案: