[Interest] QPlugin and RTTI

[Bo Thorsen]

Den 18-06-2014 15:20, Etienne Sandré-Chardonnal skrev:
> Hi,
>
> I would like to implement a plugin system in my app and I'm totally
> ignorant of dynamic library mechanisms. So I'm trying with a QPlugin.
> I'm using Qt 4.8.5, gcc 4.8.0 mingw64.
>
> The question is : can RTTI work between the plugin and the app?
>
> I will define and include these headers in both the app and the plugin:
>
> - A base class Base which will be pure virtual
> - A few DerivedA, DerivedB classes which will be pure virtual, too.
>
> Then the plugin will derive from one of the DerivedX classes, and
> provide a method in the interface which will list its implemented
> derived class names as strings, and provide a factory for them returning
> Base* objects.
>
> Then, the app will dynamic_cast these pointers to DerivedA, DerivedB, etc...
>
> Will the dynamic_cast work? Is there a special way to export/declare
> things for that?

Hi Etienne,

Yes, you can do this.

If Base is a pure interface, you can just put it in a shared header file 
and do the case. But if there is more to it, you have to put it in a 
shared library and link both the plugin and the application to it.

You can use a static library, but then stuff like singletons won't work 
reliably.

Bo.

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