initialise class members to zero

Hello!

How to write this coreactly and/or better in Delphi7?

type
	class TSomeClass
		first_var: Integer;
		// lots of vars of different types
		last_var:  Double;
		constructor Init(); override;
	end;



constructor TSomeClass.Init(); override;
begin
	FillMem(AddressOf(first_var), AddressOf(last_var)-AddressOf(first_var), 0);
	last_var := 0;
end;

Thanks