Hello all,
I'm writing a program that uses drivers for people counting devices, in
Delphi 7. The drivers are stored in BPLs, and must be loaded
dynamically, since I don't know in advance which devices will be used at
a site, and of course do not wish to recompile the application every
time a new device is introduced.
The architecture is such that all drivers inherit from a superclass
driver. The superclass driver is used in both the app and each package.
I manage to load the package dynamically (the HModule <> 0), and procede
to load the class, using an example from Delphi.
Unfortunately, when I try to use GetClass it returns nil. I register the
class as follows.
Any ideas?
Sample code is provided:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
unit MyClassUnit;
interface
uses Classes, Dialogs, SuperClassUnit;
type
TMyClass = class(TSuperClass)
published
procedure Execute(aString: String); override;
property MyResult;
end;
implementation
{ TMyClass }
procedure TMyClass.Execute(aString: String);
begin
ShowMessage(aString + '+' + FMyResult);
end;
initialization
RegisterClass(TMyClass); // <--- This is reached when the app runs
LoadPackage
end.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
unit SuperClassUnit;
interface
uses Classes;
type
TSuperClass = class(TPersistent)
private
procedure SetMyResult(const Value: String);
protected
FMyResult: String;
public
procedure Execute(aString: String); virtual; abstract;
property MyResult: String read FMyResult write SetMyResult;
end;
implementation
{ TSuperClass }
procedure TSuperClass.SetMyResult(const Value: String);
begin
FMyResult := Value;
end;
end.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
procedure TForm1.Button1Click(Sender: TObject);
type
aMyClass = class of TSuperClass;
var
phm: HModule;
AClass: TPersistentClass;
fn: String;
begin
fn:= 'MyClass';
phm:= LoadPackage(fn+'.bpl');
if phm <> 0 then
begin
AClass:= GetClass('T'+fn); // <------------------- Returns nil
if AClass <> nil then
with aMyClass(AClass).Create as TSuperClass do
begin
MyResult:= 'Bull';
Execute('Pit');
Free;
end;
UnloadPackage(phm);
end;
end;
end.
Assaf Stone
Spacelogic ltd.
[EMAIL PROTECTED]
Tel: 972-9-8855565 ext. #315
[Non-text portions of this message have been removed]
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