I don't get this syntax - do you?

[der Raab]

I understand that I'm writing very old fashioned code so I think I'm misinterpreting something very basic. Let's please talk about lines 62 to 68 in https://github.com/kevinresol/tink_http_middleware/blob/master/src/tink/http/middleware/Static.hx which I'll paste here:

var result:Promise<OutgoingResponse> = FileSystem.exists(staticPath) >>
 function(exists:Bool) return if(!exists) Future.sync(Failure(notFound)) else FileSystem.isDirectory(staticPath) >>
 function(isDir:Bool) return if(isDir) Future.sync(Failure(notFound)) else FileSystem.stat(staticPath) >>
 function(stat:FileStat) {
 var mime = mime.Mime.lookup(staticPath);
 return partial(req.header, stat, File.readStream(staticPath).idealize(function() {}), mime, staticPath.withoutDirectory());
 }

I don't get what >> does in this case. 

What I try to do is replacing Future.sync(Failure(notFound)) with a call to my new method _create404Response(): So that the server returns an 404 status if a file doesn't exist.

private function _create404Response() : OutgoingResponse {

    return new OutgoingResponse( new ResponseHeader( 404, 'Not Found', [ new HeaderField('Server', "Mine") ] ), "" );
}

I tried all kind of combinations but I either get compile time or runtime errors. 

Hm?

[Juraj Kirchheim]

The `>>` is an operator that basically takes a future and a function and tries to match up the types to produce a new future: https://haxetink.github.io/tink_core/#/types/future?id=operators

I think the code could be simplified a bit in two ways:

1. just call stat and use mode to determine if the thing is a directory (i.e. stat.mode & 0x4000 != 0)

2. use promises rather than surprises and rely on .next() rather than funky operators.

Best,

Juraj

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[der Raab]

Thanks (again!) Juraj, I read the documentation on Future operators and I try to dig thru the concepts, but right now I simply don't find where the Classes or Enums for Success() and Failure() are declared?

[der Raab]

Anyway, I figured out a way that seems to do what I want:

var result:Promise<OutgoingResponse> =

 FileSystem.exists( staticPath ) >>

  function( exists : Bool ) return FileSystem.isDirectory( staticPath ) >>

   function( isDir : Bool ) return FileSystem.stat( staticPath ) >>

    function( stat : FileStat ) {
 
     if ( exists && ! isDir ) {

      var mime = mime.Mime.lookup(staticPath);
      return partial(req.header, stat, File.readStream(staticPath).idealize(function() {}), mime, staticPath.withoutDirectory());
     }

     else {

      return _create404Response();
     }
    }

But it only worked because I made sure partial() or _create404Response() are called in the same level of "nested" Futures. Otherwise I get compile time errors. So I wonder why that is and if there would be a better way listening to Failure() and then return an 404.

This Nested Future thing looks quite abstract to me... :/

[Ben Merckx]

What you're trying to achieve can be done a bit easier: https://github.com/benmerckx/monsoon/issues/7#issuecomment-307067911

Op donderdag 8 juni 2017 15:49:36 UTC+2 schreef der Raab:

[der Raab]

THANKS!