I have a class in a unit. Usually, when I changed the algorithm of its methods, I have to recompile it and deliver the patch as a whole. I think to create the instance of the class using DLL. After searching in delphi.about.com, I found that instead of using DLL, I can use BPL. It is a DLL for Delphi. The problem is almost all examples I found is only telling how to export a function. I want to dynamically load the BPL, and whenever I replace the BPL, I can get the latest algorithm of the class, not only the functions I export.
Article I have read:
- http://delphi.about.com/od/objectpascalide/a/bpl_vs_dll.htm
- Plugins system for Delphi application - bpl vs dll?
- http://delphi.about.com/library/weekly/aa012301a.htm
Any URL or SAMPLE how to create a BPL from scratch to encapsulate a component or a class is greatly appreciated.
Dear Guru,
Suppose I have code like this:
unit unitA;
interface
type
B = class(TObject)
public
procedure HelloB;
end;
A = class(TObject)
public
function GetB: B;
function HelloA: String;
procedure Help;
end;
implementation
uses
Dialogs;
{ B }
procedure B.HelloB;
begin
ShowMessage('B');
end;
{ A }
function A.GetB: B;
begin
Result := B.Create;
end;
function A.HelloA: String;
begin
Result := 'Hello, this is A';
end;
procedure A.Help;
begin
//do something
end;
end.
I want to export all public methods of A. How to make it a DLL? How to use it from another unit where to import it? let's say:
var a: A;
a := A.Create;
a.GetB;
showMessage(a.HelloA);
A is not declared in the unit (it is in the DLL). Please advise.
Hurray. I got it last night. All I have to do is make the object implement an interface which is used in the caller unit to catch the instance of object returned by the DLL.
Thank you all.