From kde-multimedia  Sun Sep 19 08:38:59 2004
From: Marco Lohse <mlohse () cs ! uni-sb ! de>
Date: Sun, 19 Sep 2004 08:38:59 +0000
To: kde-multimedia
Subject: Re: kdemm backends & Helix
Message-Id: <414D45A3.2050509 () cs ! uni-sb ! de>
X-MARC-Message: https://marc.info/?l=kde-multimedia&m=109558307227098

Matthias Welwarsky wrote:
[..]

>  
>
>As a sidenote, this is also how plugins are accessed in Trolltechs Qtopia 
>environment. Basically, you are guaranteed that each plugin implements a 
>queryInterface() method which can be asked by means of a UUID: " do you 
>support this interface?". In case of a match, queryInterface() returns  a 
>pointer to an instance implementing said interface, or a null pointer in case 
>of a mismatch. Of course you need to static_cast<> the pointer you receive.
>
>  
>
Just a short remark:

NMM provides 'built-in' support for such things using its 
object-oriented interface system. You can ask any plug-in what 
interfaces (i.e. what functionality) it supports, e.g.:

INode* readfile = graph.getINode(readfile_descr);
IFileHandler_var filehandler (readfile-> getParentObject()-> getCheckedInterface<IFileHandler> ());
filehandler-> setFilename(argv[1]);

(the _var type is just a C++ auto_ptr<>)

=> tries to get the interface IFileHandler from the plug-in node 
readfile. When using the 'checked' get interface method, if this 
interface is not available, an InterfaceNotFoundExceotion is thrown. Or 
you can use getInterface<IFileHandler>() which will return a null 
pointer in this case.

Have fun, Marco.

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