On Thursday, 6 June 2024 at 17:49:39 UTC, Andy Valencia wrote:
I was using instance initialization which allocated a new
object. My intention was this initialization would happen
per-instance, but all instances appear to share the same
sub-object? That is, f1.b and f2.b appear to point to a single
object? Obviously I moved the new into the initializer code,
but I hadn't appreciated how initial instance values were
calculated once. Interestingly, this makes it similar to how
Python calculates default argument values for functions.
class Bar {
int z = 3;
}
class Foo {
auto b = new Bar();
}
void
main() {
import std.stdio : writeln;
auto f1 = new Foo(), f2 = new Foo();
f1.b.z = 0;
writeln(f2.b.z);
}
This is a long standing issue:
https://issues.dlang.org/show_bug.cgi?id=2947
I think with the next edition we can disallow (tail) mutable
initializers for fields (and TLS globals too).
