On Friday, 1 May 2015 at 11:01:29 UTC, Chris wrote:
On Friday, 1 May 2015 at 10:47:22 UTC, Chris wrote:
On Friday, 1 May 2015 at 10:46:20 UTC, Chris wrote:
On Friday, 1 May 2015 at 10:27:16 UTC, biozic wrote:
On Friday, 1 May 2015 at 10:12:36 UTC, Chris wrote:
On Friday, 1 May 2015 at 10:04:46 UTC, Namespace wrote:
How about this:
----
struct A {
int x = 42;
}
struct B {
int x = 7;
}
T factory(T)() {
return T();
}
void main()
{
auto a = factory!(A);
}
----
That's what I was looking for, I just couldn't get it
right. Thanks.
Rikki:
I wanted to avoid classes and interfaces.
This might be a bit more useful:
---
struct A {
int x = 42;
}
struct B {
int x = 7;
}
auto factory(string type = "")() {
static if (type == "A")
return A();
else static if (type == "B")
return B();
else
return A(); // default
}
void main()
{
auto a = factory!"A";
auto b = factory!"B";
auto x = factory;
}
---
Duh, I tried `static if` yesterday and I still got "Error:
mismatched function return type inference of B and A". Now it
works! Sure, I must have overlooked something. Sometimes it's
better to go home and call it a day than to try to get
something to work.
And thanks, by the way!
Thinking about it,
T factory(T)() {
return T();
}
is better suited for a factory (with static type checks).
But then I don't know what factory!X() provides that X() alone
doesn't.
This aside, how would I get something to load dynamically? It's
either "mismatched function return type" or (with type check)
"variable X cannot be read at compile time":
void main(string[] args) {
auto type = args[1];
auto myType = factory!type();
}
So it's back to classes/interfaces again? Hmmmm.
Indeed. Runtime polymorphism is based on classes and interfaces.
The struct and template solutions can only make "compile-time
factories".
