When using the TpFIBDataSet, I do not seem to find a way to handle INT64 types. Help please

Question: When using the TpFIBDataSet, I do not seem to find a way to handle INT64 types. Help please.

Field "PROD_UNIT_PRICE" in Firebird = BigInt     =  2,200,000,000

Delphi
pFIBDSDetail=TpFIBDataSet

var
mfact:int64;
...
case pfibqreport.fieldbyname('TBL_Type').AsInteger of
4: mfact:=pFIBDSDetail.fieldbyname('PROD_UNIT_PRICE').AsInteger

my result=
pFIBDSDetail.fieldbyname('PROD_UNIT_PRICE').AsInteger comes through as -2094967296

There is not
pFIBDSDetail.fieldbyname('PROD_UNIT_PRICE').asint64

How do I pass an Int64 through a TpFIBDataSet?

Answer:
Method "Fieldbyname" returns abstract class "TField". This class haven't methods for work with Int64 values.

pFIBDataSet has the psUseLargeIntField option in PrepareOptions. If
you include it into your code then FB Bigint field will do mapping
to TFIBLargeIntField. In this case you must write your code as:
4: mfact:=TFIBLargeIntField( pFIBDSDetail.fieldbyname('PROD_UNIT_PRICE')).AsLargeInt

If you don't include psUseLargeIntField then this field will do mapping to TFIBBCDField.

In this case you should write your code as:
4: mfact:=TFIBBCDField( pFIBDSDetail.fieldbyname('PROD_UNIT_PRICE')).AsInt64

And the last recommendation... If you can't know about prepareOptions in your code then you can write it as:
4:
  if pFIBDSDetail.fieldbyname('PROD_UNIT_PRICE') is  TFIBBCDField then
    mfact:=TFIBBCDField( pFIBDSDetail.fieldbyname('PROD_UNIT_PRICE')).AsInt64
  else
  mfact:=TFIBLargeIntField( pFIBDSDetail.fieldbyname('PROD_UNIT_PRICE')).AsLargeInt