ZIO，入门，纯功能下载器

Question

I have a simple program that is more or less a downloader. It collect one or many configurable resources (via a custom protocol), aggregate and write them in on place.

This program seems simple but the code is still complex and mix functional and procedural code (from my Java background). I would like to simplify it and move to an fully functional one. I am reading about ZIO and the whole picture start to build in my head.

However, after having read the getting started and the overview I still have some questions.

The main flow may be like :

for {
  config    <- Configuration.parse(args)
  resources <- Downloaders.download(config)
  _         <- Writer.write(resources)
} yield ()

1. I guess the configuration that contains static values but also one http client will be put into ZIO Environment .

2. The downloaders may be effects built from a future and may use the ZIO bracket to close the connection. I guess that I can aggregate the results with fold . But I don't know how to create and execute many downloaders.
   Edited a) Since Future are note pure, how can I model a effect that will run asynchronously (I plan to use Play Standalone WS Client) ?
   Edited b) I should create one downloader per target, the request will be assigned to them. But how should I implement that in my code ? Should I create a ZIO[Configuration, Throwable, List[Downloader]] and then, later, execute all of them via collectAllPar ?

3. I have no idea on how to write the aggregation on disk.

I would like to use this project to promote ZIO internaly. So I would like to use the best options and cleanest approach. Can someone give me some tips on how to implement those effects and structure my code ? Edited: Should I build my system on the ZIO components or build a set of functions and wrap them into the ZIO effects ?

Thanks a lot

Answer 1

Your question is not very specific which means that unfortunately it won't attract high-quality answers.

I will still try to answer some of the points.

• Future s are not pure. If possible, avoid them.
• Your donwloader will be a function Request => ZIO[R, E, Response] . To make them run in parallel, use ZIO.collectAllPar or ZIO.zip . The result is a ZIO[R, E, List[A]] or a ZIP[R, E, TupleX[...]] , which you can store in resources in your for-comprehension.
• Writing data to a file can be done with Scala's new PrintWriter(new File("hello.txt")) wrapped into, you guessed it, a ZIO.bracket .

For more insights into program design with ZIO I would suggest reading Beautiful, Simple, Testable Functional Effects for Scala from De Goes himself.

Also, of course, refer to the documentation found on ZIO's website .