Re: Does anyone understand how to use "shared" types with concurrency send/receive functions?

[Kagamin via Digitalmars-d-learn]

On Monday, 14 August 2017 at 22:22:58 UTC, Arek wrote:

I've found some simple workaround for this problem:

import std.stdio;
import std.concurrency;

struct Envelope(T) if (is(T == class)) // for simplicity of this example, only classes

{
        shared(T)[] obj;

        this(shared T o)
        {
                this.obj = [o];
        }

        T get() @property nothrow @nogc
        {
                return cast() obj[0];
        }
}

class A
{

}

void consumer()
{
        auto r = receiveOnly!(Envelope!(A))();
        writeln("Got: ", typeof(r).stringof);
}

void main()
{
        auto cons = spawn(&consumer);
        auto o = Envelope!A(new A());
        send(cons, o);
}

Shared object can be encapsulated in the array. In case of other (non-class) types the pointer can be used, and get() should return ref to the pointed object (after stripping off the shared qualifier).

Rather like this:

struct Sendable(T)
{
        shared T o;
        alias o this;
}

import std.concurrency;

class A
{
        int method() shared;
}

void consumer()
{
        shared A a = receiveOnly!(Sendable!(A))();
}

void producer()
{
        auto cons = spawn(&consumer);
        shared A a = new shared A();
        send(cons, Sendable!A(a));
}