Re: Referance usage in async function

[aliak via Digitalmars-d-learn]

On Saturday, 30 November 2019 at 13:45:00 UTC, kerdemdemir wrote:
I have simplified my problem which can be seen below.
import std.stdio;
import vibe.core.core;
import vibe.core.concurrency;
import vibe.data.json;

void main()
{
    int[] list;

    bool ListManipulator(ref int[] list)
    {
        list ~= 2;
        list ~= 4;
        return true;
    }

    bool ListManipulatorPointer( int[]* list)
    {
        *list ~= 2;
        *list ~= 4;
        return true;
    }


    auto future = vibe.core.concurrency.async(&ListManipulator, 
list);
    future.getResult();

    writeln(list); ----> prints empty list

    future = 
vibe.core.concurrency.async(&ListManipulatorPointer, &list);
    future.getResult();

    writeln(list); ----> prints [2,4]
}


Why passing the pointer works meanwhile passing as reference 
does nothing? I feel that is more D issue than vibe.d which I 
can learn something I hope.

Erdem

Looks like a bug in vibe: 
https://github.com/vibe-d/vibe-core/blob/master/source/vibe/core/concurrency.d#L1141

The function async doesn't use auto ref on ARGS. So the arguments 
are value copies through. If it used auto ref all the way through 
then it'd probably work:

---
import std;

void async(CALLABLE, ARGS...)(CALLABLE callable, auto ref ARGS 
args) {
    callable(args);
}

void main() {
    int[] list;
    bool ListManipulator(ref int[] list) {
        list ~= 2;
        list ~= 4;
        return true;
    }

    async(&ListManipulator, list);
    writeln(list);
}