Call different member functions on object sequence with a generic handler function?

[Basile B.]

On Saturday, 30 June 2018 at 00:16:49 UTC, Basile B. wrote:
> On Friday, 29 June 2018 at 16:44:36 UTC, Robert M. Münch wrote:
>> I hope this is understandable... I have:
>>
>> class C {
>> 	void A();
>> 	void B();
>> 	void C();
>> }
>>
>> I'm iterating over a set of objects of class C like:
>>
>> foreach(obj; my_selected_objs){
>> 	...
>> }
>>
>> The iteration and code before/afterwards always looks the 
>> same, I need this iteration for many of the memember functions 
>> like C.A() and C.B(), etc.
>>
>> foreach(obj; my_selected_objs){
>> 	...
>> 	obj.A|B|C()
>> 	...
>> }
>>
>> So, how can I write a generic handler that does the iteration, 
>> where I can specify which member function to call?
>>
>> void do_A() {
>> 	handler(C.A()); ???
>> }
>>
>> void do_B() {
>> 	handler(C.B()); ???
>> }
>>
>> handler(???){
>> 	foreach(obj: my_selected_objs){
>> 		???
>> 	}
>> }
>>
>> Viele Grüsse.
>
> Using opDispatch we can manage to get a voldemort able to 
> resolve the member func A, B or C etc.
>
> ---
> import std.stdio;
>
> class C
> {
>     void A(){writeln(__FUNCTION__);}
>     void B(int i){writeln(__FUNCTION__, " ", i);}
> }
>
> auto handler(T)(T t)
> {
>     struct Handler
>     {
>         auto opDispatch(string member, Args...)(Args args)
>         {
>             import std.algorithm.iteration : each;
>             mixin( `t.each!(a => a.` ~ member ~ `(args));` );
>         }
>     }
>     Handler h;
>     return h;
> }
>
> void main()
> {
>     auto cs = [new C(), new C()];
>     handler(cs).A();
>     cs.handler.B(42); // UFCS style
> }
> ---
>
> which results a very natural expression.

insert "in" at the right place.