Question

I have a group of functions that use Sub-Range types for their input parameter.

const
  ImprovementNodeCount = 20;
  SaleAllocationNodeCount = 10;

type   
  TImprovementNodePrintOrders = 0..ImprovementNodeCount;
  TSaleAllocationNodePrintOrders = 0..SaleAllocationNodeCount;


  function SaleImprovementType(PrintOrder: TImprovementNodePrintOrders): TSaleReferenceRecord;

  function SaleAllocationType(PrintOrder: TSaleAllocationNodePrintOrders): TSaleReferenceRecord;
  function SaleAllocationAcres(PrintOrder: TSaleAllocationNodePrintOrders): TSaleReferenceRecord;
  // many more functions with different SubTypes

This has been working very well for me. I have a new situation where it would be convenient to pass one of these functions as a parameter. My sub-ranges are now causing problems because they are different types.

All of the functions look the same except for the sub-type. I tried to add a new function type like this

  TGetReferenceFunction = function (Index: cardinal): TSaleReferenceRecord;

Right now the compiler complains that the types are different when I try to pass the function parameter as a TGetReferenceFunction. Is there any way to create a function type that will include all of these functions that have different sub-type parameters?

[DCC Error] SaleNameMap.pas(295): E2010 Incompatible types: 'Cardinal' and 'TImprovementNodePrintOrders'

What I really need is a type that is all numeric sub-types. I know I can create a different function type for each sub-type I have, but that still will not let me pass these functions as parameters into one common function.

I’m guessing this is not possible. If so I have some other options, but in case there is something I am missing I thought I would try here first.

Answer 1

If you really want one function to accept all those distinct function types, then you’ll have to sacrifice type safety. You can do this with a cast:

TGetReferenceFunction(@SaleAllocationAcres)