Hello,
I have read several times that alias this is a way to implement inheritance for
structs.
I am simply unable to imagine how to use this feature that way. Has anyone an
example?
As I understand it, alias this constructs a proxy that delegates some or all of
of its behaviour to its 'alias' member. Full stop. How, from this, can one
construct for instance such a minimalistic subtyping hierarchy --and make it
work as expected:
struct S {
bool b;
}
struct SI {
bool b;
int i;
void write () { writeln("int: ", this.i); }
}
struct SF {
bool b;
float f;
void write () { writeln("float: ", this.f); }
}
unittest {
auto si = SI(true, 1);
si.write();
auto sf = SF(false, 1.1);
sf.write();
// challenge:
S[2] a;
a[0] = si; a[1] = sf;
foreach (s ; a) s.write();
}
The equivalent using class subtyping would be trivial (indeed):
class C {
bool b;
void write() {};
}
class CI : C {
int i;
this (int i) { this.i = i; }
override void write () { writeln("int: ", this.i); }
}
class CF : C {
float f;
this (float f) { this.f = f; }
override void write () { writeln("float: ", this.f); }
}
unittest {
auto ci = new CI(1);
ci.write();
auto cf = new CF(1.1);
cf.write();
// works:
C[2] a; a[0] = ci; a[1] = cf;
foreach (c ; a) c.write();
}
Help welcome, thank you,
Denis
--
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