我想知道在使用 sequenceT 时是否可以“扩大”我的终极阅读器类型?这在使用 chainW 等按顺序链接操作时是可能的,但看起来在使用 sequenceT 时,您会遇到每个项目都必须使用相同的 Reader 类型。我想这样做,这样我就可以在适当的地方并行执行一些任务,但仍然可以通过 Reader 使用依赖注入。
例子:
import { sequenceT } from 'fp-ts/lib/Apply'
import { log } from 'fp-ts/lib/Console'
import { pipe } from 'fp-ts/lib/function'
import * as RT from 'fp-ts/ReaderTask'
interface Person {
name: string
}
const getMe = (name: string) => (deps: { api: any }) => async (): Promise<Person> => {
const person = {
name,
}
return person
}
const getMum = (child: Person) => (deps: { api2: any }) => async (): Promise<Person> => {
const person = {
name: child.name + "'s mum",
}
return person
}
const getDad = (child: Person) => (deps: { api2: any }) => async (): Promise<Person> => {
const person = {
name: child.name + "'s dad",
}
return person
}
const getFamily = (name: string) =>
pipe(
getMe(name),
RT.chainW(me =>
sequenceT(RT.readerTask)(
getMum(me),
getDad(me))
))
getFamily('John')({ api: 'x', api2: 'y' })().then(
([mum, dad]) => {
log(mum)()
log(dad)()
})
这可以很好地编译并输出:
$ node dist/src/index.js
{ name: "John's mum" }
{ name: "John's dad" }
现在假设 getDad 依赖于不同的 api,比如 api3。如果我更新它不再编译的代码,因为 getMum 和 getDad 没有使用相同的 Reader 类型。
示例(不编译):
import { sequenceT } from 'fp-ts/lib/Apply'
import { log } from 'fp-ts/lib/Console'
import { pipe } from 'fp-ts/lib/function'
import * as RT from 'fp-ts/ReaderTask'
interface Person {
name: string
}
const getMe = (name: string) => (deps: { api: any }) => async (): Promise<Person> => {
const person = {
name,
}
return person
}
const getMum = (child: Person) => (deps: { api2: any }) => async (): Promise<Person> => {
const person = {
name: child.name + "'s mum",
}
return person
}
const getDad = (child: Person) => (deps: { api3: any }) => async (): Promise<Person> => {
const person = {
name: child.name + "'s dad",
}
return person
}
const getFamily = (name: string) =>
pipe(
getMe(name),
RT.chainW(me =>
sequenceT(RT.readerTask)(
getMum(me), // compiler complains here
getDad(me))
))
getFamily('John')({ api: 'x', api2: 'y', api3: 'z' })().then( // compiler complains here, on api3
([mum, dad]) => {
log(mum)()
log(dad)()
})
我实际上是在用 StateReaderTaskEither 尝试这个,但在这个例子中简化了它以使用 ReaderTask - 然而,sequenceT 也表现出相同的限制。
任何想法如何解决?