Swift cannot convert the expression's type 'Void' to type 'String!' -

i'm trying use piece of sample code this nshipster article, halfway down page.

var inputstream: nsinputstream var outputstream: nsoutputstream  nsstream.getstreamstohostwithname(hostname: "nshipster.com",                                       port: 5432,                                inputstream: &inputstream,                               outputstream: &outputstream) 

i've placed in playground, along import foundation, , error.

playground execution failed: error: <repl>:6:10: error: cannot convert expression's type 'void' type 'string!' nsstream.getstreamstohostwithname(hostname: "nshipster.com", ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

this error pointing first argument, of type string! , not void.

i changed code bit, extract definitions method call. here's complete playground:

import foundation  var inputstream: nsinputstream var outputstream: nsoutputstream  let host = "nshipster.com" let port = 5432 nsstream.getstreamstohostwithname(hostname: host,     port: port,     inputstream: &inputstream,     outputstream: &outputstream) 

now error indicates third argument, presumably happy first two.

playground execution failed: error: <repl>:10:18: error: cannot convert expression's type 'void' type 'inout nsinputstream' inputstream: &inputstream,              ^~~~~~~~~~~~ 

i can't figure out how can extract autoreleasingunsafepointer variables inputstream , outputstream in same manner, think original sample code should work. bug in (and mattt's) code, or bug in swift?

edit: i've submitted pull request corrected code nshipster.

well, short answer need passing in optionals instead of non-optionals (to that's looking inout objects)

var inputstream:nsinputstream? var outputstream:nsoutputstream?  nsstream.getstreamstohostwithname("nshipster.com", port: 5432, inputstream: &inputstream, outputstream: &outputstream) 

that said, compiles now, doesn't run because nsstream apparently doesn't have getstreamstohostwithname method (at least in foundation imported) never mind this, it's ios-only call, didn't work playground set osx. seems ok set ios.