using shared effectively in a producer/consumer situation.

[Kevin Balbas via Digitalmars-d-learn]

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?