Re: passing subclass to superclass where parameter is a delegate for the superclass
On Wednesday, 14 November 2018 at 16:39:52 UTC, Alex wrote:
Are you looking for this?
https://dlang.org/phobos/std_traits.html#TransitiveBaseTypeTuple
It matches however not exactly your needs:
As all objects are derived from the Object class, you will
always get it as the common parent. So... with the trait, you
get a list but have still to make a decision which type to use.
Maybe, something like this:
´´´
import std.traits;
template properBase(T)
{
static foreach(i, t; TransitiveBaseTypeTuple!A)
{
static if(hasMember!(t, "add_function")){}
else
{
static if(!__traits(compiles, {auto c =
properBase.init;}))
{
alias properBase =
TransitiveBaseTypeTuple!A[i-1];
}
}
}
}
void main(){}
class base
{
void delegate(typeof(this)) stored_dg;
this(){}
void
add_function (void delegate (typeof(this)) dlg)
{
stored_dg = dlg;
}
}
class A : base
{
alias pB = properBase!A;
this ()
{
super ();
add_function ();
}
void foo (pB a)
{
import std.experimental.logger;
log ("i got here");
}
}
´´´
Re: passing subclass to superclass where parameter is a delegate for the superclass
On Wednesday, 14 November 2018 at 16:06:21 UTC, Chris Bare wrote:
If I have:
class base
{
void delegate(base) stored_dg;
void
add_function (void delegate (base) dlg)
{
stored_dg = dlg;
}
}
class A : base
{
this ()
{
super ();
add_function ();
}
void foo (A a)
{
log ("i got here");
}
}
it fails because foo(A) does not match the parameter type of
delegate(base)
If I change foo (A a) to foo (base a)
It works, but this could be awkward in a deeper class hierarchy
where you
might not know the class name to use.
Is there a way to do this where foo's parameter type does not
to match the
class that implements add_function?
Thanks,
Chris
Are you looking for this?
https://dlang.org/phobos/std_traits.html#TransitiveBaseTypeTuple
It matches however not exactly your needs:
As all objects are derived from the Object class, you will always
get it as the common parent. So... with the trait, you get a list
but have still to make a decision which type to use.
passing subclass to superclass where parameter is a delegate for the superclass
If I have:
class base
{
void delegate(base) stored_dg;
void
add_function (void delegate (base) dlg)
{
stored_dg = dlg;
}
}
class A : base
{
this ()
{
super ();
add_function ();
}
void foo (A a)
{
log ("i got here");
}
}
it fails because foo(A) does not match the parameter type of
delegate(base)
If I change foo (A a) to foo (base a)
It works, but this could be awkward in a deeper class hierarchy
where you
might not know the class name to use.
Is there a way to do this where foo's parameter type does not to
match the
class that implements add_function?
Thanks,
Chris
