[pclasses-devel] Factory: key aliasing support added

[stephan b. <st...@s1...>]

This is an interesting little feature:

  typedef Factory<MyType> F;
  F & f = F::instance();
  f.registerFactory( "MyType", MyType::createNewInstance );
  f.alias( "AnAlias", "MyType" );
  MyType * m = f.create( "AnAlias" );

Since PluginManager extends Factory, we can do some more subtle tricks 
with it, like aliasing DLL names or simulating symlinks by 
aliasing /P/plugins/mypluginname to /real/path/to/mypluginname.so. Or 
alias http://path/to/s11n/data to ~/foo.s11n (or vice versa).
Setting up a "virtual filesystem" to factories/DLLs this way might be 
really interesting to consider: /P/plugins, /P/devices, /P/protocols...
That would require slighty different aliasing support (the current 
support is word-based, whereas /P/... effectively needs partial string 
search support).

Anyway...

There's *all kinds* of evil we can do with this. :)

This has some nice benefits for code maintenance: we can use aliases in 
code and allow the user to re-map their own types to those aliases via 
config files and whatnot. For example, in client code we write:

DocumentType * d = f.create( "default-document-class" );

The factory could expect "default-document-class" to come from the 
DocumentPluginManager, which reads ~/.myapprc (or equivalent) to get 
the info. For example, the user maps this in his configuration data:
   default-document-class = MySpecialDocType

During plugin initialization, the DocumentPluginManager simply converts 
config info to:

   Factory<Document>.alias( default-document-class", 
"MySpecialDocType" );

MySpecialDocType must, of course, be linked in or be found in 
MySpecialDocType.{so,dll}.



-- 
----- st...@s1...   http://s11n.net
"...pleasure is a grace and is not obedient to the commands
of the will." -- Alan W. Watts