组合scalaz io效果对象

我试图使用scalaz的ioeffect IO[E，A]monad作为一段非常有效的代码

我试图用IO[E，A]在高层重写的代码包含了一些关于存储在云中的文件的元数据。代码试图：

下载该文件

从文件中提取字符串

构建包含文件文本内容的pojo

将pojo提交到某个队列/restful服务

这些步骤的细节并不重要，但我想做的是按照以下思路做一些事情：

def processShareActivity(fileObject: FileObject): IO[ProcessFileFailure, IndexResponse] = {
    for {
        file <- downloadFile (fileObject)
        text <- extractText (file)
        searchFileObject <- IO.point(buildSearchFileObject (fileObject, file, text))
        indexedResponse <- indexSearchFileObject (searchFileObject)
    } yield indexedResponse
}

def indexSearchFileObject(fileObject: SearchFileObject): IO[IndexFailure, IndexResponse] = ???

def buildSearchFileObject(fileObject: FileObject, file: File, str: String): SearchFileObject = ???

def extractText(file: File): IO[ExtractionFailure, String] = ???

def downloadFile(fileObject: FileObject): IO[DownloadFileFailure, File] = ???

def processShareActivity（fileObject:fileObject）：IO[ProcessFileFailure，IndexResponse]={
为了{
文件不幸的是，您确实需要一种方法来将这些错误统一为一个常见错误：

例如：

sealed trait ProcessFileFailure
object ProcessFileFailure {
   case class Index(e: IndexFailure) extends ProcessFileFailure
   case class Extraction(e: ExtractionFailure) extends ProcessFileFailure
   case class Download(e: DownloadFileFailure) extends ProcessFileFailure
}

你的理解力将变成：

for {
        file <- downloadFile (fileObject).leftMap(ProcessFileFailure.Download)
        text <- extractText (file).leftMap(ProcessFileFailure.Extraction)
        searchFileObject <- IO.point(buildSearchFileObject (fileObject, file, text))
        indexedResponse <- indexSearchFileObject (searchFileObject).leftMap(ProcessFileFailure.Index)
    } yield indexedResponse

用于{
文件