What is the "right" way to create a generic type getter (and setter) ?

[James Blachly]

On Wednesday, 14 March 2018 at 22:58:25 UTC, ag0aep6g wrote:
> You can probably get around the (manually maintained?) `FIELDS` 
> array with `.tupleof` or something similar:
>
> ----
> static foreach (i, f; S.tupleof)
> {
>     case __traits(identifier, f):
> }
> ----
>
>> Any pointers / design patterns on this particular type of 
>> problem class would be greatly appreciated.  (Sidenote, I 
>> realize I could probably use the witchcraft library, but I am 
>> also using this as exercise to learn D beyond the basics).
>
> You simply cannot have a method that returns different types 
> based on a run-time value. You could possibly return a 
> std.variant.Variant. But if the goal is just to print the value 
> to the screen, all you need is a string.
>
> So the signature would be `string get(string field)`. And for 
> the implementation you could use `.tupleof` to iterate over all 
> fields, and then return `f.to!string`.
>
> `set` can be done similarly. Take two `string`s: the field 
> name, and the value. `static foreach` over all fields. On a 
> match, convert the given value string to the type of the field 
> that matched.

Thanks - to!string certainly seems to be a good option in this 
case (CLI) and I was definitely overthinking this part, perhaps 
because I was trying to write everything as generically / 
extensibly as possible (for example, to use the same framework 
but with a GUI or web front end, for example).

I would still think an AA mapping (string) field name to a type 
would be useful and will see if I can construct it as a mixin 
using typeof(Struct.member) somehow.