Re: how to get value of object's field from second thread?

[r3d9u11]

Thanks!

Re: how to get value of object's field from second thread?

[mashingan]

You forgot `initLock`.

Also since you just only toggle the boolean value, you may consider to use 
[cas](https://nim-lang.org/docs/system.html#cas,ptr.T,T,T)

Re: how to get value of object's field from second thread?

[r3d9u11]

well, "\--threadAnalysis:off"+globalvar+lock looks nice: 


import os, threadpool, locks

type
  MyObj = ref object
flag: bool

var olock: Lock
var obj {.guard: olock.}: MyObj

proc someThread() {.gcsafe.} =
  {.locks: [olock].}:
if obj != nil:
  echo obj.flag
  obj.flag = false

obj.new()
obj.flag = true
spawn someThread()
sleep 500
echo obj.flag

Re: how to get value of object's field from second thread?

[r3d9u11]

Thanks, I saw your examples in previous posts with similar theme (I've post 
link before). Well, I did "simple" application, who demonstrate exchanging 
process of object between two threads. This model looks it is logical, but code 
looks really mad and inflexible  (for 21th), sorry: 


import os, threadpool

type
  SharedChannel[T] = ptr Channel[T]

proc newSharedChannel[T](): SharedChannel[T] =
  result = cast[SharedChannel[T]](allocShared0(sizeof(Channel[T])))
  open(result[])

proc close[T](ch: var SharedChannel[T]) =
  close(ch[])
  deallocShared(ch)
  ch = nil

proc send[T](ch: SharedChannel[T], content: T) =
  ch[].send(content)

proc recv[T](ch: SharedChannel[T]): T =
  result = ch[].recv

type
  MyObj = ref object
flag: bool

proc someThread(ch: SharedChannel[MyObj]) {.thread.} =
  var obj = ch.recv
  if obj != nil:
echo obj.flag
obj.flag = false
  ch.send(obj)

var
  ch = newSharedChannel[MyObj]()
spawn someThread(ch)
var obj: MyObj
obj.new()
obj.flag = true
ch.send(obj)
sleep 500
obj = ch.recv
echo obj.flag
close(ch)


Now I'll figure out how best to integrate this model into the application. 
Thanks for all for your help and discussion!

Re: how to get value of object's field from second thread?

[mashingan]

For simply passing value, use 
[channels](https://nim-lang.org/docs/channels.html) .

Looking at your case, I guess you should use channels. You have two separate 
thread, first is qml thread and 2nd server thread.

Using channel, you can apply producer-consumer pattern to both.

Re: how to get value of object's field from second thread?

[r3d9u11]

I trying to do workaround for [this 
issue](https://github.com/filcuc/nimqml/issues/21) and also try to understand, 
how to correctly pass data beetween threads in Nim for future projects (in 
other languages I had not any difficulties or problems with this ).

Re: how to get value of object's field from second thread?

[twetzel59]

Oops.

`loopThr` needs a loop, or the program will exit immediately.

Re: how to get value of object's field from second thread?

[twetzel59]

I think I should note that I'm not sure if you really intended using `async*` 
with threadpools. Async stuff in Nim is still single threaded (even though its 
concurrent, it is not parallel).

You should instead use a single-threaded program, declare `loopThr` as 
`{.async.}` and then use `await` in `loopThr`.

Please let me know if you need any help with the `async` stuff, it can indeed 
be a bit weird...

I can't test this now, but try: 


type
  Server* = ref object
socket: AsyncSocket
started*: bool
...
...

proc newServer*(): Server =
  Server(
socket: nil,
false,
...
  )

proc loopThr(server: Server, serverPort: int) {.async.} =
  server.socket = newAsyncSocket()
  server.socket.bindAddr(serverPort.Port)
  server.socket.listen()
  server.started = true
  # server.loopTask = loop(server) # not sure what this is here
  # waitFor server.loopTask # you can do some non-blocking IO now. eg:
  let line = await server.socket.recvLine() # this will not block

proc start*(server: Server, serverPort: int) =
  waitFor loopThr(server, serverPort) # changed this to ``waitFor`` for 
example's sake.
  sleep(100)

Re: how to get value of object's field from second thread?

[r3d9u11]

How to do it correctly and, probably, elegantly? (sorry, but constructions like 
[this](https://forum.nim-lang.org/t/1572/2#9868) looks a bit mad for this easy 
task  I tried something like a: 


import os, threadpool

type
  MyObj = object
flag: bool

proc subThr(pObj: ptr MyObj) {.gcsafe.} =
  pObj.flag = true

var pShr = cast[ptr MyObj](allocShared0(sizeof(MyObj)))

var o: MyObj = pShr[]
o.flag = false
spawn subThr(pShr)
sleep 100
echo o.flag


But it's don't write data by pointer. Maybe somebody have ideas?

Re: how to get value of object's field from second thread?

[mashingan]

in your case, it would be sharing memory, share variable between threads and 
modify it atomically or through mutex.