I have an application where a long-lived "loader" thread takes messages to load data, loads that data, and then sends it back to the main thread via the standard concurrency primitives.  Something like this:

void threadFunc(Tid ownerTid)
{
    while(true)
    {
        receive(
            (int id, string path) { LoadThingByPath(ownerTid, id, path); }
        );
    }
}

void LoadThingByPath(Tid ownerTid, int id, string path)
{
    ret thing = MakeThing(path)
    send(ownerTid, id, thing);
}



I know I need to make thing shared, but I don't know how do it properly in this context.  Casting to shared in send() works, but then I have to accept a shared Thing on the other side, process it as a shared Thing, etc.  cast(Thing) doesn't appear to cast away the shared qualifier either.  Does that mean ALL of the loaded data in my application needs to be shared all the time?  Is there not simply a way to transfer ownership?

On Sunday, 23 April 2017 at 20:30:33 UTC, Kevin Balbas wrote:
> I have an application where a long-lived "loader" thread takes messages to load data, loads that data, and then sends it back to the main thread via the standard concurrency primitives.  Something like this:
>
> void threadFunc(Tid ownerTid)
> {
>     while(true)
>     {
>         receive(
>             (int id, string path) { LoadThingByPath(ownerTid, id, path); }
>         );
>     }
> }
>
> void LoadThingByPath(Tid ownerTid, int id, string path)
> {
>     ret thing = MakeThing(path)
>     send(ownerTid, id, thing);
> }
>
>
>
> I know I need to make thing shared, but I don't know how do it properly in this context.  Casting to shared in send() works, but then I have to accept a shared Thing on the other side, process it as a shared Thing, etc.  cast(Thing) doesn't appear to cast away the shared qualifier either.  Does that mean ALL of the loaded data in my application needs to be shared all the time?  Is there not simply a way to transfer ownership?

And after two hours of fiddling with this in a simple project I notice a bug that kept me from casting away shared.  Please disregard that part.

I guess the follow up here is:  Is this the correct way to do it?  cast to shared, send to main thread, cast away shared?

On Sunday, 23 April 2017 at 20:33:48 UTC, Kevin Balbas wrote:

> I guess the follow up here is:  Is this the correct way to do it?
>  cast to shared, send to main thread, cast away shared?

At the moment, pretty much yes. Either that or make the (unnecessary) immutable copies.
There are no ownership primitives in Phobos yet, and shared itself is still... not quite there.

On Sunday, 23 April 2017 at 20:33:48 UTC, Kevin Balbas wrote:
> Is this the correct way to do it?
>  cast to shared, send to main thread, cast away shared?

Yes, as long as the thing is unique, you can cast it to shared or immutable just fine.