jo***********@gmail.com wrote:
I have a program that is going to have plugins used for various
capabilities. The main program creates a class (AppCore) which
handles everything. This class contains another class (PluginController)
that handles loading the shared objects via the dl* functions. When I
create the plugins, I link them using -shared.
The plugins themselves are derived from a class (Plugin)... inside of
the Plugin class there is a variable to hold a pointer back to the
AppCore object. This is so the plugins can call various functions
from AppCore object created at start up.
Should I have to link in the AppCore.o the plugins when I'm creating
them? It seems like it wont work unless I do that.. I'm not sure I
understand why I need to link those in.. shouldn't the main program
export those symbols?
The problem with this is that it introduces cyclic dependencies (bad
thing). i.e., AppCore depends on PluginController, and
PluginController depends on AppCore (to pass the pointer to the plugins
when loaded). You will have something like this:
,---------. ,------------------.
| |------->| |
| AppCore | | PluginController |
| |<-------| |
`---------' `------------------'
One solution is to have a pure virtual interface (e.g., AppInterface),
that provides all the methods that plugins would need to call in the
applications. Have AppCore implement this interface and just pass the
pointer to AppInterface. That way, your dependency diagram looks like
this:
,---------. ,--------------. ,------------------.
| AppCore |---->| AppInterface |<----| PluginController |
`---------' `--------------' `------------------'
Your linker will thank you for it :)
Hope this helps,
-shez-
