Question

im currently working in a simple program that implements plugins whith dll libraries (using the TJvPluginManager from the JVCL Framework).

So far I figure out how to use this component to handle commands but what if i want to have a return value from a custom function inside the library?. It is posible to call a certain function from the host by using the TJvPluginManager? How should I implement this?.

The hole idea is to have a function that returns a string inside each dll so it can be called by using a simple cicle. I think I can do this by hand (using dinamic loading) but I want to work with TJvPluginManager as much as possible.

Thank you for your time.
John Marko

Answer 1

The way I do it is to implement an Interface in the plugin and call it from the host e.g.

MyApp.Interfaces.pas

uses
  Classes;

type
  IMyPluginInterface = interface
  ['{C0436F76-6824-45E7-8819-414AB8F39E19}']
    function ConvertToUpperCase(const Value: String): String;
  end;

implmentation

end.

The plugin:

uses
  ..., MyApp.Interfaces;

type
  TMyPluginDemo = class(TJvPlugIn, IMyPluginInterface)
  public
    function ConvertToUpperCase(const Value: String): String;
  ...

implmentation

function TMyPluginDemo.ConvertToUpperCase(const Value: String): String;
begin
  Result := UpperCase(Value);
end;

...

The host:

uses
  ..., MyApp.Interfaces;

...

function TMyHostApp.GetPluginUpperCase(Plugin: TjvPlugin; const Value: String): String;
var
  MyPluginInterface: IMyPluginInterface;
begin
  if Supports(Plugin, IMyPluginInterface, MyPluginInterface) then
    Result := MyPluginInterface.ConvertToUpperCase(Value)
  else
    raise Exception.Create('Plugin does not support IMyPluginInterface');
end;

Hope this helps.