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" */
}
----

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();
}

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.

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.

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.