在流中扩展对象类型和覆盖属性

Question

在TypeScript中，我可以执行以下操作：

interface MyObj {

    a: 'foo' | 'bar'

}

interface MyExtObj extends Pick<MyObj, Exclude<keyof MyObj, 'a'>> {

    a: MyObj['a'] | 'baz'

}

const test: MyExtObj = {

    a: 'baz' // Works fine, as well as 'foo' and 'bar'

}

是否可以使用Flow对象类型执行此操作，如果可以，如何执行？以下示例失败...

/* @flow */

type MyObj = {

    a: 'foo' | 'bar'

}

type MyExtObj = MyObj & {

    a: $PropertyType<MyObj, 'a'> | 'baz'

}

const test: MyExtObj = {

    a: 'baz' // Cannot assign object literal blah blah ...

}

Answer 1

像这样？/* @flow */type MyObj = {|&nbsp; &nbsp; a: 'foo' | 'bar'|}type MyExtObj = {|&nbsp; &nbsp; ...MyObj,&nbsp; &nbsp; a: $PropertyType<MyObj, 'a'> | 'baz'|}const test: MyExtObj = {&nbsp; &nbsp; a: 'baz' // Cannot assign object literal blah blah ...}

Answer 2

如果由于某些原因您不想精确设置MyObj，这也可以使用：/* @flow */type MyObj = {&nbsp; &nbsp; a: 'foo' | 'bar'}type MyExtObj = {|&nbsp; &nbsp; ...$Exact<MyObj>,&nbsp; &nbsp; a: $PropertyType<MyObj, 'a'> | 'baz'|}const test: MyExtObj = {&nbsp; &nbsp; a: 'baz' // Cannot assign object literal blah blah ...}