Converting member variables to strings with using reflection from base class

[Mengu]

On Friday, 22 December 2017 at 22:09:05 UTC, H. S. Teoh wrote:
> On Fri, Dec 22, 2017 at 09:13:31PM +0000, kerdemdemir via 
> Digitalmars-d-learn wrote:
>> I want to make a logging function for member variables by 
>> using reflection.
> [...]
>> class B
>> {
>>     void Log()
>>     {
>>         auto a = [__traits(derivedMembers, D)];
>>         foreach(memberName; a) {
>>             // Somehow write only member variables with their 
>> names
>>             // Result should be : a = 4.0, b = 3.0
>
> Try this:
>
> 	import std.traits : FieldNameTuple;
> 	foreach (memberName; FieldNameTuple!B) {
> 		writefln("%s = %s", memberName, mixin("this." ~ memberName));
> 	}
>
>
> T

and then turn it into a LoggerMixin with a mixin template and 
re-use it any time you want.

import std.stdio : writeln, writefln;
import std.traits : FieldNameTuple;

mixin template LoggerMixin() {
   void Log() {
     foreach (memberName; FieldNameTuple!(typeof(this))) {
       writefln("%s = %s", memberName, mixin("this." ~ 
memberName));
     }

   }
}

struct S {
   int x;
   bool y;
   double z;

   mixin LoggerMixin;
}

void main() {

   S s1 = S(int.min, true, 6666);
   S s2 = S(int.max, false, 6666);
   s1.Log();
   s2.Log();
}