• Quirin Schroll (5/5) May 02 2023 How do I invoke the member function in a reliable way? Given
• ag0aep6g (20/25) May 02 2023 Construct a delegate from the alias and the object, and call that delega...
• Nick Treleaven (7/14) May 03 2023 This also works:
• ag0aep6g (4/21) May 03 2023 No, it doesn't. You're not using the alias. You're just accessing
• Nick Treleaven (2/12) May 03 2023 Sorry, you're right.
• Steven Schveighoffer (4/9) May 02 2023 Isn't that what `__traits(child)` is for?
• Adam D Ruppe (4/6) May 03 2023 Yes, __traits(child, object, method_alias)(args) is the way to do
• Quirin Schroll (22/29) May 04 2023 This doesn’t work, but a slight modification does the trick:

Quirin Schroll <qs.il.paperinik gmail.com> writes:

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.)

ag0aep6g <anonymous example.com> writes:

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 = &method;
     dg.ptr = cast(void*) c;
     dg();
}

void main()
{
     fun!(C.method)(new C); /* prints "42" */
}
----

Nick Treleaven <nick geany.org> writes:

On Tuesday, 2 May 2023 at 13:06:41 UTC, ag0aep6g wrote:
 void fun(alias method)(C c)
 {
     void delegate() dg;
     dg.funcptr = &method;
     dg.ptr = cast(void*) c;
     dg();
 }

This also works:

void fun(alias method)(C c)
{
     void delegate() dg = &c.method;
     dg();
}

ag0aep6g <anonymous example.com> writes:

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 = &method;
     dg.ptr = cast(void*) c;
     dg();
 }

 
 This also works:
 
 void fun(alias method)(C c)
 {
      void delegate() dg = &c.method;
      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.

Nick Treleaven <nick geany.org> writes:

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 = &c.method;
      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.

Steven Schveighoffer <schveiguy gmail.com> writes:

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

Adam D Ruppe <destructionator gmail.com> writes:

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.

Quirin Schroll <qs.il.paperinik gmail.com> writes:

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)`.