Delphi typed constants in case statements

Question

What is the most elegant (or least ugly) way of using typed constants in a case statement in Delphi?

That is, assume for this question that you need to declare a typed constant as in

const
  MY_CONST: cardinal = $12345678;
  ...

Then the Delphi compiler will not accept

case MyExpression of
  MY_CONST: { Do Something };
  ...
end;

but you need to write

case MyExpression of
  $12345678: { Do Something };
  ...
end;

which is error-prone, hard to update, and not elegant.

Is there any trick you can employ to make the compiler insert the value of the constant (preferably by checking the value of the constant under const in the source code, but maybe by looking-up the value at runtime)? We assume here that you will not alter the value of the "constant" at runtime.

Take out ": cardinal". Problem solved. You do NOT need to use TYPE DECLARATIONS and in fact you need to NOT use them. — Warren P
Yes, I know. But I explicitly wrote "assume for this question that you need to declare a typed constant as in"... — Andreas Rejbrand

Uli Gerhardt Uli Gerhardt · Accepted Answer · 2010-06-08T17:44:44

Depending on why you need the constant to be typed you can try something like

const
  MY_REAL_CONST = Cardinal($12345678);
  MY_CONST: Cardinal = MY_REAL_CONST;

case MyExpression of
  MY_REAL_CONST: { Do Something };
  ...
end;

Delphi typed constants in case statements

3 Answers