Re: [Vala] Ref parameters to async methods

[Jim Peters <jim uazu net>]

Nor Jaidi Tuah wrote:
> Is there any technical reason why
> reference parameters are not supported for async methods?
>
> My work around to this is simply to replace
>   async void foo (ref X x)  // cannot compile
>
> with
>   async void foo (ClosureX cx)
> where Closure is
>   class ClosureX {
>      X x;
>   }
>
> But why can't the compiler do this for us?
> I must be missing something.

I think the problem is that 'ref' is for both input and output, but
async methods put the input arguments into the .begin() call, and the
output arguments into the .end() call.  So where should the 'ref'
argument go?  It can't go in both places.

If you only need output, then use 'out' instead.  If you need both
input and output I think you'll have to use two arguments.

As the other poster said, the scope containing the variable you 'ref'
in the call will probably have completely gone by the time it is
written to, so (if it were allowed) you'd risk crashing your app due
to corrupting the stack by using 'ref' with async.

Jim

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