On Thursday, 9 June 2016 at 22:19:33 UTC, Stretto wrote:
I have some class like
class bar { }
class foo : bar
{
bar[] stuff;
}
and have another class
class dong : bar
{
int x;
}
Now sometimes stuff will contain dong's, but I cannot access
its members it without a cast.
fooo.stuff[0].x // invalid because bar doesn't contain x;
Hence,
((cast(dong)foo.stuff[0]).x is the normal way with a possible
type check.
But in my case I will never mix different types in stuff and
will always use it properly or do type checking in the cases I
might mix.
That's just the nature of working with class hierarchies. A
Derived is always a Base, but a Base might not be a Derived. If
your Bar array in Foo will always hold only one type of Bar, then
you can parameterize Foo with a type:
###########################
class Bar { }
// Only accept types that are implicitly convertible to Bar
class Foo(T : Bar) : Bar
{
T[] stuff;
}
class Dong : Bar
{
int x;
this(int x) { this.x = x; }
}
void main()
{
import std.stdio;
auto foo = new Foo!Dong();
foo.stuff ~= new Dong(10);
writeln(foo.stuff[0].x);
}
###########################
Another option is to use a parameterized getter, which is
somewhat cleaner than a cast.
###########################
class Foo : Bar
{
Bar[] stuff;
T get(T : Bar)(size_t index)
{
return cast(T)stuff[index];
}
}
void main()
{
import std.stdio;
auto foo = new Foo();
foo.stuff ~= new Dong(10);
writeln(foo.get!Dong(0).x);
}
###########################
