/usr/lib/python2.7/dist-packages/epsilon/modal.py is in python-epsilon 0.7.1-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 | # -*- test-case-name: epsilon.test.test_modes -*-
import new
class ModalMethod(object):
"""A descriptor wrapping multiple implementations of a particular method.
When called on an instance, the implementation used will be
selected based on an attribute of the instance. There are no
unbound ModalMethods at this point.
@ivar name: The name of this method.
@ivar methods: A mapping of modes to callable objects.
@ivar modeAttribute: The name of the attribute on instances which
is bound to the instance's current mode.
"""
def __init__(self, name, methods, modeAttribute):
self.name = name
self.methods = methods
self.modeAttribute = modeAttribute
def __get__(self, instance, owner):
if instance is None:
raise AttributeError(self.name)
try:
mode = getattr(instance, self.modeAttribute)
except AttributeError:
raise AttributeError(
"Mode attribute %r missing from %r, "
"cannot get %r" % (self.modeAttribute, instance, self.name))
try:
func = self.methods[mode]
except KeyError:
raise AttributeError(
"Method %r missing from mode %r on %r" % (self.name, mode, instance))
return new.instancemethod(func, instance, owner)
class mode(object):
"""
Base class for mode definitions. Subclass this in classes of type
ModalType and provide the implementations of various methods for
that particular mode as methods of the mode subclass. The
subclass should have the same name as the mode it is defining.
"""
# XXX fix the simple, but wrong, __dict__ magic in ModalType.__new__ so
# that this __enter__ and __exit__ are actually called, maybe we can even
# do some logging or something.
def __exit__(self):
"""
The mode has just been exited.
"""
def __enter__(self):
"""
The mode has just been entered.
"""
def _getInheritedAttribute(classname, attrname, bases, attrs):
try:
return attrs[attrname]
except KeyError:
for base in bases:
try:
return _getInheritedAttribute(classname, attrname,
base.__bases__,
base.__dict__)
except TypeError:
pass
else:
raise TypeError('%r does not define required attribute %r' %
(classname,
attrname))
class ModalType(type):
"""Metaclass for defining modal classes.
@type modeAttribute: C{str}
@ivar modeAttribute: The attribute to which the current mode is
bound. Classes should not define the attribute this names; it
will be bound automatically to the value of initialMode.
@type initialMode: C{str} (for now)
@ivar initialMode: The mode in which instances will start.
"""
def __new__(cls, name, bases, attrs):
modeAttribute = _getInheritedAttribute(name, 'modeAttribute', bases, attrs)
initialMode = attrs['initialMode'] = _getInheritedAttribute(name, 'initialMode', bases, attrs)
# Dict mapping names of methods to another dict. The inner
# dict maps names of modes to implementations of that method
# for that mode.
implementations = {}
keepAttrs = {'mode': initialMode}
for (k, v) in attrs.iteritems():
if isinstance(v, type) and issubclass(v, mode):
for (methName, methDef) in v.__dict__.iteritems():
if methName not in ('__module__', '__file__', '__name__'):
implementations.setdefault(methName, {})[k] = methDef
keepAttrs[k] = v
for (methName, methDefs) in implementations.iteritems():
keepAttrs[methName] = ModalMethod(methName, methDefs, modeAttribute)
return super(ModalType, cls).__new__(cls, name, bases, keepAttrs)
class Modal(object):
__metaclass__ = ModalType
modeAttribute = 'mode'
initialMode = 'nil'
class nil(mode):
def __enter__(self):
pass
def __exit__(self):
pass
def transitionTo(self, stateName):
self.__exit__()
self.mode = stateName
self.__enter__()
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