Question

Given a record type:

TItem = record
   UPC : string[20];
   Price : Currency;
   Cost : Currency;
   ...
end; 

And the name of a field as a string, how can I get the offset of that field within the record? I need to do this at runtime – the name of the field to access is decided at runtime.

Example:

var
   pc : Integer;
   fieldName : string;
   value : Currency;
begin
   pc := Integer(@item);                    // item is defined and filled elsewhere
   fieldName := Text1.Text;                 // user might type 'Cost' or 'Price' etc
   Inc(pc, GetItemFieldOffset(fieldName));  // how do I implement GetItemFieldOffset?
   value := PCurrency(pc)^;
   ..

I’m using Delphi 7.

Answer 1

You can’t. Delphi 7 does not emit RTTI for records. There are other options (as seen the previous answers) but those require manual mapping of “Field Name” -> “Offset”.