Re: Passing a class instance to a thread via spawn()

[Ali Çehreli]

On 07/18/2013 04:23 PM, Joseph Rushton Wakeling wrote:
> Hello all,
>
> I have a data structure which is a final class.  Once created, the 
contents of
> the class will not be mutated (only its const methods will be called).
>
> Is there any way to pass this to a thread via spawn() or via 
message-passing?
> I've seen instructions to use shared() but if I try and declare the 
class this
> way I get errors such as "non-shared method is not callable using a 
shared
> object" and "non-shared const method is not callable using a shared 
object".
>
> The ideal would be to mark this object, once created, as immutable -- 
but trusty
> methods like assumeUnique() don't work for classes!
>
> Can anyone advise?
>
> Thanks & best wishes,
>
>       -- Joe
>

The following seems to work but it may have more 'immutable' keywords 
than you need. For example, the final class F need not be 'immutable'. I 
think it is the objects of it that you want 'immutable'. (?)

Anyway, the following may be a start:

import std.concurrency;
import core.thread;

interface I
{
    int foo();
}

class C : I
{
    int i;

    this(int i) immutable {
        this.i = i;
    }

    override int foo() {
        return 1;
    }
}

immutable final class F : C
{
    double d;

    this(int i, double d) immutable {
        super(i);
        this.d = d;
    }

    /* 'override' keyword is required if the class is non-immutable
     * and not required otherwise. Bug? */
    int foo() {
        return 2;
    }

    int bar() const {
        return 3;
    }
}

void worker(immutable(F) f)
{
    f.bar();
}

void main()
{
    auto f = new immutable(F)(42, 1.5);

    spawn(&worker, f);

    thread_joinAll();
}

Ali