class NamedDescriptor(object):
def __init__(self):
# Name of the attribute, will be set by the classes with
# the meta class DescriptorNameGetterMetaClass
self.name = None
def __get__(self, obj, type=None):
if obj:
# at the moment, we return the name of the descriptor,
# you can change this line to adapt to your needs
return self.name
else:
return self
def __set__(self, adaptor, value):
if adaptor:
# change the name, you can change this line to adapt to your needs
self.name = value
else:
raise AttributeError('Cannot set this value')
class NamedDescriptorResolverMetaClass(type):
'''
This is where the magic happens.
'''
def __new__(cls, classname, bases, classDict):
# Iterate through the new class' __dict__ and update all recognised NamedDescriptor member names
for name, attr in classDict.iteritems():
if isinstance(attr, NamedDescriptor):
attr.name = name
return type.__new__(cls, classname, bases, classDict)
class DescriptorHost(object):
'''
The Descriptor gets its name automatically even before any instance of the class is created,
thanks MetaClass!
>>> DescriptorHost.myFunDescriptor.name
'myFunDescriptor'
In our case, the NamedDescriptor returns it's name when being looked for from the host instance:
>>> dh = DescriptorHost()
>>> dh.myFunDescriptor
'myFunDescriptor'
'''
__metaclass__ = NamedDescriptorResolverMetaClass
myFunDescriptor = NamedDescriptor()
if __name__ == "__main__":
import doctest
doctest.testmod()
Diff to Previous Revision
--- revision 2 2010-10-19 22:25:50
+++ revision 3 2010-10-19 22:55:16
@@ -21,7 +21,11 @@
class NamedDescriptorResolverMetaClass(type):
+ '''
+ This is where the magic happens.
+ '''
def __new__(cls, classname, bases, classDict):
+ # Iterate through the new class' __dict__ and update all recognised NamedDescriptor member names
for name, attr in classDict.iteritems():
if isinstance(attr, NamedDescriptor):
attr.name = name
