Article #17677: Passing a function to a procedure or vice versa.

 Question and Answer Database
FAQ2677D.txt Passing a function to a procedure or vice versa.
Category :Object Pascal
Platform :All
Product :All 32 bit
Question:
Can I pass a function or procedure to another function or
procedure?
Answer:
Yes. You must declare a procedure or function type to use
as the parameter type, then you can pass the address of the
procedure that you wish to pass. You must be careful to
pass functions or procedures that are compatible with the
function or procedure expected, as little error checking
will be provided by the compiler.
Example:
type
AFunctionType = function(IntIn : integer) : integer;
function AddProc(IntIn : integer) : integer;
begin
Result := IntIn + 1;
end;
function SubProc(IntIn : integer) : integer;
begin
Result := IntIn — 2;
end;
procedure PassAFunction(var IntIn : integer;
fn : AFunctionType);
begin
IntIn := fn(IntIn);
end;
procedure TForm1.Button1Click(Sender: TObject);
var
i : integer;
begin
i := 10;
PassAFunction(i, @AddProc);
ShowMessage(IntToStr(i));
PassAFunction(i, @SubProc);
ShowMessage(IntToStr(i));
end;
7/16/98 4:31:28 PM

Last Modified: 01-SEP-99