[Qt-interest] QObject based plugins

[michael.goddard at nokia.com]

> Let me rephrase my question then:
> I have a series of interfaces that plugins can implement. 
> There is one 
> main, basic interface, and a series of smaller, secundairy interfaces 
> that the plugins can *additionally* implement. These interfaces are 
> defined in a header that is included from the main codebase by the 
> plugins. I am using QPluginLoader::instance() and the 
> Q_DECLARE_INTERFACE and Q_INTERFACES macro's to define and load the 
> plugins.
> Is there some way to make my primairy interface QObject derived, so I 
> can define the needed signals and slots in the interface?

Perhaps not the exact answer, but another way to do this is to have your plugin interface just be a factory interface for your actual QObject derived classes.

E.g.:

class MyPlugin : public Qobject
{
	Q_OBJECT
public slots:
	void doSomething(MyOtherObject* bar);
signals:
	void didSomething(int baz);
};

class MyPluginFactory
{
	virtual ~MyPluginFactory() {}
	virtual MyPlugin* MyPluginInterface() const = 0;
};

Q_DECLARE_INTERFACE(MyPluginFactory, "my plugin factory");

For the multiple interface inheritance part of things, well.. That won't work if each interface needs to be a QObject for the signals and slots, but you might be able to have multiple interface functions in the "factory".  Internally those objects would probably share state somehow.  It is a bit messy :/

E.g.

class MyInterface1 : public QObject {}
class MyInterface2 : public QObject {}
class MyInterface3 : public QObject {}

class MyPluginWrapper
{
	virtual ~MyPluginWrapper() {}
	virtual MyInterface1* interface1() const = 0;
	virtual MyInterface2* interface2() const = 0;
	virtual MyInterface3* interface3() const = 0;
}
Q_DECLARE_INTERFACE(MyPluginWrapper, "My Plugin Wrapper");

I'm sure you could come up with a scheme somewhat like COM this way :)

Cheers,
MichaelG

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