I use this code to get member function address on runtime:

=========
struct A {
       this(){};
}
auto ctor = (&__traits(getMember, A.init,"__ctor")).funcptr;
=========


my question is, how to get it in compile time like static function address:

=========
struct A {
     void d(){};
     static void fn(){};
}

enum FN = &A.fn;  // static method address is ok
enum A0 = &(A.d).funcptr; // Error: need this for d of type void()
enum A1 = (&__traits(getMember, A,"d")).funcptr; // Error: no property funcptr for type void function()
enum A2 = (&__traits(getMember, A.init,"d")).funcptr; //  Error: (&A().d).funcptr cannot be evaluated at compile time
=========

On Thursday, 19 March 2020 at 04:30:32 UTC, Calvin P wrote:
> I use this code to get member function address on runtime:
>
> =========
> struct A {
>        this(){};
> }
> auto ctor = (&__traits(getMember, A.init,"__ctor")).funcptr;
> =========
>
>
> my question is, how to get it in compile time like static function address:
>
> =========
> struct A {
>      void d(){};
>      static void fn(){};
> }
>
> enum FN = &A.fn;  // static method address is ok
> enum A0 = &(A.d).funcptr; // Error: need this for d of type void()
> enum A1 = (&__traits(getMember, A,"d")).funcptr; // Error: no property funcptr for type void function()
> enum A2 = (&__traits(getMember, A.init,"d")).funcptr; //  Error: (&A().d).funcptr cannot be evaluated at compile time
> =========

A non-static member method can use the context of the struct where it is defined in. E.g. it could alter a member variable.
This context has to be constructed at run time (and there could be many instances of the context) and does not exist in compile time. Therefore the difference to the static method.

On Thursday, 19 March 2020 at 04:30:32 UTC, Calvin P wrote:
> I use this code to get member function address on runtime:
>
> =========
> struct A {
>        this(){};
> }
> auto ctor = (&__traits(getMember, A.init,"__ctor")).funcptr;
> =========
>
>
> my question is, how to get it in compile time like static function address

You asked the same question two days ago.
Check the reply.
https://forum.dlang.org/post/r4ohd3$2e94$1@digitalmars.com

You can assemble a delegate with an struct pointer or class reference and a function member pointer.

On Thursday, 19 March 2020 at 06:34:40 UTC, Alex wrote:
> A non-static member method can use the context of the struct where it is defined in. E.g. it could alter a member variable.
> This context has to be constructed at run time (and there could be many instances of the context) and does not exist in compile time. Therefore the difference to the static method.

I am not try to get the context, I just need the function address which is const and should able to get at compile time.


On Thursday, 19 March 2020 at 09:13:42 UTC, Boris Carvajal wrote:
> On Thursday, 19 March 2020 at 04:30:32 UTC, Calvin P wrote:
>
> You can assemble a delegate with an struct pointer or class reference and a function member pointer.

Sorry for duplicate thread.

The last time I submit my question on web, it keep get blocked. I thought it was not submitted successfully, so I submit from draft again.

On Thursday, 19 March 2020 at 04:30:32 UTC, Calvin P wrote:
> my question is, how to get it in compile time like static function address:
>
> =========
> struct A {
>      void d(){};
>      static void fn(){};
> }
>
> enum FN = &A.fn;  // static method address is ok
> enum A1 = (&__traits(getMember, A,"d")).funcptr; // Error: no property funcptr for type void function()

Check the error message there... you already have a function pointer, no need to use the .funcptr metod.

It is a bit weird though because it actually EXCLUDES the hidden argument for `this`. I prefer doing wrapper functions usually.

On Thursday, 19 March 2020 at 13:23:41 UTC, Adam D. Ruppe wrote:
>
> Check the error message there... you already have a function pointer, no need to use the .funcptr metod.
>
> It is a bit weird though because it actually EXCLUDES the hidden argument for `this`. I prefer doing wrapper functions usually.


Thanks for the tips,   I can get it into enum but not be able to use it as const at compile time. I come up with this workaround:


static void* getCallee() pure @nogc nothrow {
		enum callee_ptr = &(__traits(getMember, App, name));
		return callee_ptr;
}

__gshared const AppHelper  APP_HELPER = {&getCallee,  ..};