How Do I create a data type that can contain either Real or String?

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I'm trying to create something like System.TVariant. I can't use TVariant because it stores the data in a type which it thinks it should be, i.e it will store a small number in another type than Real... Anyways, if there is a workaround for that, I don't want that, I just want to know 'how' it works and how I can create a data type that can hold varying data types, Something like this:

Delphi

type
  TStrInt = (AnsiString or Integer);

var
  TVr: TStrInt;

begin
  TVr := 56;
  WriteLn(TVr);
end.

As you can see, the 'or' gives error, and so does 'TVr := 56'. Anyway to do this?

Posted 16-Sep-15 2:43am

Nafees Hassan

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2 solutions

Solution 1

I guess you have to use a Variant Record, see, for instance "Storing groups of data together"[^].

Posted 16-Sep-15 3:06am

CPallini

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Sergey Alexandrovich Kryukov 16-Sep-15 10:27am

This is a different thing, my 5 for mentioning it. However, I think the root problem is very different: I see no justification in using variants here. Please see Solution 2. Yes, it's based just on some claims, but it's not so easy to provide logical evidence in a Quick Answer...
—SA

CPallini 16-Sep-15 10:57am

Thank you.

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-09-16T04:25:00

Listen for a good friendly advice: never ever use Variants, unless they are required by some 3rd-party lame API. Imaginary benefits of this type is a pretty usual delusion which damages part of developers. Delphi and many other technologies are oriented to strong typing, https://en.wikipedia.org/wiki/Strong_and_weak_typing[^].

Don't get me wrong, different typing paradigms, such as loose typing, can be extremely productive, especially in some scripting (interpretive) languages, but trust me, most of such technologies are way better than the lame COM variants. Also, COM is badly obsolete, there is no a reason to follow its worst drawbacks.

—SA