[fpc-pascal] Unrelated type helpers with the same members? Implement an interface with a type helper?

[Michael Van Canneyt]

On Fri, 23 Dec 2022, Sven Barth via fpc-pascal wrote:

> Michael Van Canneyt via fpc-pascal <fpc-pascal at lists.freepascal.org>
> schrieb am Fr., 23. Dez. 2022, 08:18:
>
>>
>>
>> On Thu, 22 Dec 2022, Andrew Haines via fpc-pascal wrote:
>>
>>> Hi what I want to do is similar to this question here:
>>>
>> https://en.delphipraxis.net/topic/423-rtti-determine-record-helper-type-for-a-base-type/
>>>
>>> I am going to create multiple type helpers for enums and I would like to
>> look
>>> up the helper and use common methods AsString AsOrdinal to get/set the
>>> values. I am recieving them as json that I dont have control over. I am
>> using
>>> typeinfo to fill in all the properties but I would like to convert the
>>> strings I am receiving to the enum values semi-automatically.
>>>
>>> LString := 'STATUS';
>>>
>>> LHelper := GetHelper(LPropInfo^.PropType); // enum proptype
>>
>> Since there can be multiple type helpers for a type, this will never be
>> possible. At best you would get a list.
>>
>> But I don't think there is even a list of type helpers per type.
>> Sven will need to confirm.
>>
>
> As the active helper(s) for a type change(s) depending on the current scope
> (e.g. in unit A it might be a different helper than in unit B) this is not
> possible. Also helpers are not in any way usable on their own except to
> retrieve their RTTI information.

But theoretically it should be possible to generate and get a list of all 
defined type helpers, whether they are in scope or not ?

If their RTTI could include a function that returns an interface, you could
retrieve that and do as the OP suggests...

I think the OP's solution with attributes is the same as the one TMS Software's
Aurelius ORM uses.

Michael.