CALL FUNCTIONS FROM LIST OF FUNCTIONS HELD IN TABLE
Folks,
I don't know where this topic is at the moment, but here is an example that
I have used. The functions/procedures are not internal to the Delphi EXE,
but are stored in a Delphi DLL (nearly as good).
I have created a list of functions in a table. All the functions have the
same parameters and return values. Using this, I can create a function (or
procedure definition) in the routine used to call the function, as follows:
function CallFunction(const LibraryName, FunctionName: String): Integer;
var
f: function: Integer;
h: THandle;
begin
{ load library }
h := LoadLibrary(PChar(LibraryName));
{ if library loaded }
if h <> 0 then
begin
try
{ call function }
@f := GetProcAddress(h, PChar(FunctionName));
if @f <> nil then
Result := f;
{ free library }
finally
FreeLibrary(h);
end;
end;
end;
Admittedly, you need to know the structure (parameters and results) of each
type of function/procedure you create, but you can define these as a 'type',
as follows (see Dynamic Loading - DLL's - in the Delphi help for v4):
TReportFunction = procedure(var StartDate, EndDate: TDateTime);
You could then store the name of the library and functions in a table, load
them dynamically and pass them to the above routine. I do this at a client
site, where I have a list or reports in a libary, and to add a new report I
simply add a record to the database and send them a new DLL, or a new
version of the report DLL that has the new report in it. The calling EXE
doesn't need to be touched.
I hope this helps,
Darren
P.S. I too am an ex Clipper developer, and noticed that a few Clipper people
seemed to move to Delphi when Nantucket missed the Windows market. I
remember fondly the ability to call functions and procedures on the fly, and
recently tried to do it in Delphi. I managed to do it for the method of a
class, but couldn't find a way to locate the address of a procedure or
function. Does anyone know if this is possible, or am I talking bull ?
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