On Friday, 17 January 2014 at 17:50:54 UTC, H. S. Teoh wrote:
On Fri, Jan 17, 2014 at 05:29:14PM +0000, Gary Willoughby wrote:
On Friday, 17 January 2014 at 15:56:46 UTC, H. S. Teoh wrote:
>Couldn't you just return a Variant? I thought this is what
>Variants
>are made for.
>
>
>T
Yes but then i would need to coerce it to get it's underlying
type.
But isn't that what you'd have to do anyway? I mean, how else
would the
following code work?
class DynClass {
...
auto opDispatch(string field)() {
return dotDotDotMagic();
}
}
void main(string[] args) {
auto d = new DynClass();
if (args[1] == "int")
d.abc = 123; // d.abc = int
else
d.abc = "xyz"; // d.abc = string
// Suppose this somehow works:
auto x = d.abc; // what's the type of x?
}
Since the type of x must be known at compile-time, but the type
of d.abc
can't be known until runtime, the above code can't possibly
work unless
d.abc returns a Variant. It's simply not possible for a
runtime-determined type to be put into a variable of
compile-time
determined type without some kind of runtime check.
Now I'm not sure if Variant allows assignment to a static type,
but in
theory this should be possible:
// assume d.abc returns a Variant
int x = d.abc; // will assert if d.abc doesn't hold an int at
runtime
T
In the example in my original post the types are known at compile
time but they are different between properties. I wondered if
there was a solution to storing and retrieving while preserving
the original type via opDispatch.
I have a working solution but it only stores the base type. So i
f i have an inheritance chain like this:
A -> B -> C
I can store properties of type A, B and C but when i retrieve
them they all come back as A because of array covariance. I
wonder if there is a way of casting them automagically to the
correct type.
