[Twisted-Python] twisted.plugin plugin framework

[Matt Goodall]

Nathaniel Haggard wrote:
> 1.  What is/was the purpose of twisted.plugin?  

It is for loading plugins! ;-)

> 
> 2.  "mypkg" is a directory containing __init__.py
> 
> __init__.py contains:
> 
> import twisted.plugin
> import zope.interface as z
> import twisted.plugin as p
> 
> class Beta:
>         z.implements(p.IPlugin)
> 
> class Gamma:
>         """This is the doc string"""
> 
>         __implements__ = p.IPlugin
> 
> -----------------
> 
> Trying to load the package with getPlugins returns an empty generator
> as far as I can tell

OK, the main thing is that t.plugin loads *instances* of IPlugin
implementing classes. It does not find classes with an implements(IPlug)
and create instances for you.

Something like:

    class Beta:
        z.implements(p.IPlugin)

    betaPlugin = Beta()

will /probably/ be enough for t.plugin to find them. However, you almost
certainly want your plugins to implement another, application specific,
more interesting interface too, i.e.

    class ISomething(Interface):
        pass

    class Beta:
        z.implements(p.IPlugin, ISomething)

    betaPlugin = Beta()

You can then search for ISomething plugins, which is much more
meaningful than searching for any (i.e IPlugin) plugin.

    plugins = twisted.plugin.getPlugins(ISomething, mypkg)

Hope that helps.

Cheers, Matt

> 
> 
> import twisted.plugin
> import mypkg
> 
> l = twisted.plugin.getPlugins(twisted.plugin.IPlugin, mypkg)
> print dir(l)
> for i in l:
>         .....
> 
> Actually twisted.plugin.getCache doesn't return anything for
> getPlugins to get.  Am I setting up the package incorrectly?
> 
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