Re: Given an object, how to call an alias to a member function on it?
On Wednesday, 3 May 2023 at 11:38:46 UTC, Adam D Ruppe wrote:
On Tuesday, 2 May 2023 at 13:57:23 UTC, Steven Schveighoffer
wrote:
Isn't that what `__traits(child)` is for?
https://dlang.org/spec/traits.html#child
Yes, `__traits(child, object, method_alias)(args)` is the way
to do it.
This doesn’t work, but a slight modification does the trick:
```d
--- a.d
#line 3 "a.d" // for run.dlang.io
struct S
{
private void f() {}
}
alias Sf = S.f;
--- b.d
#line 12 "b.d" // for run.dlang.io
import a;
void main()
{
S s;
__traits(child, s, Sf)(); // error: Error: struct `a.S`
function `f` is not accessible
(&__traits(child, s, Sf))(); // ok
}
```
Thanks for making me aware of `__traits(child)`.
Re: Given an object, how to call an alias to a member function on it?
On Wednesday, 3 May 2023 at 11:26:00 UTC, ag0aep6g wrote:
On 03.05.23 13:13, Nick Treleaven wrote:
void fun(alias method)(C c)
{
void delegate() dg =
dg();
}
No, it doesn't. You're not using the alias. You're just
accessing `c.method` directly. If the actual method weren't
called "method", you'd get an error.
Sorry, you're right.
Re: Given an object, how to call an alias to a member function on it?
On Tuesday, 2 May 2023 at 13:57:23 UTC, Steven Schveighoffer wrote: Isn't that what `__traits(child)` is for? https://dlang.org/spec/traits.html#child Yes, __traits(child, object, method_alias)(args) is the way to do it.
Re: Given an object, how to call an alias to a member function on it?
On 03.05.23 13:13, Nick Treleaven wrote:
On Tuesday, 2 May 2023 at 13:06:41 UTC, ag0aep6g wrote:
void fun(alias method)(C c)
{
void delegate() dg;
dg.funcptr =
dg.ptr = cast(void*) c;
dg();
}
This also works:
void fun(alias method)(C c)
{
void delegate() dg =
dg();
}
No, it doesn't. You're not using the alias. You're just accessing
`c.method` directly. If the actual method weren't called "method", you'd
get an error.
Re: Given an object, how to call an alias to a member function on it?
On Tuesday, 2 May 2023 at 13:06:41 UTC, ag0aep6g wrote:
void fun(alias method)(C c)
{
void delegate() dg;
dg.funcptr =
dg.ptr = cast(void*) c;
dg();
}
This also works:
void fun(alias method)(C c)
{
void delegate() dg =
dg();
}
Re: Given an object, how to call an alias to a member function on it?
On 5/2/23 8:52 AM, Quirin Schroll wrote:
How do I invoke the member function in a reliable way? Given `obj` of
the type of the object, I used `mixin("obj.", __traits(identifier,
memberFunc), "(params)")`, but that has issues, among probably others,
definitely with visibility. (The member function alias is a template
parameter.)
Isn't that what `__traits(child)` is for?
https://dlang.org/spec/traits.html#child
-Steve
Re: Given an object, how to call an alias to a member function on it?
On 02.05.23 14:52, Quirin Schroll wrote:
How do I invoke the member function in a reliable way? Given `obj` of
the type of the object, I used `mixin("obj.", __traits(identifier,
memberFunc), "(params)")`, but that has issues, among probably others,
definitely with visibility. (The member function alias is a template
parameter.)
Construct a delegate from the alias and the object, and call that delegate:
class C
{
int field = 42;
void method() { import std.stdio; writeln(field); }
}
void fun(alias method)(C c)
{
void delegate() dg;
dg.funcptr =
dg.ptr = cast(void*) c;
dg();
}
void main()
{
fun!(C.method)(new C); /* prints "42" */
}
Given an object, how to call an alias to a member function on it?
How do I invoke the member function in a reliable way? Given
`obj` of the type of the object, I used `mixin("obj.",
__traits(identifier, memberFunc), "(params)")`, but that has
issues, among probably others, definitely with visibility. (The
member function alias is a template parameter.)
