Source code for sqlobject.declarative

Declarative objects.

Declarative objects have a simple protocol: you can use classes in
lieu of instances and they are equivalent, and any keyword arguments
you give to the constructor will override those instance variables.
(So if a class is received, we'll simply instantiate an instance with
no arguments).

You can provide a variable __unpackargs__ (a list of strings), and if
the constructor is called with non-keyword arguments they will be
interpreted as the given keyword arguments.

If __unpackargs__ is ('*', name), then all the arguments will be put
in a variable by that name.

You can define a __classinit__(cls, new_attrs) method, which will be
called when the class is created (including subclasses).  Note: you
can't use super() in __classinit__ because the class isn't bound to a
name.  As an analog to __classinit__, Declarative adds
__instanceinit__ which is called with the same argument (new_attrs).
This is like __init__, but after __unpackargs__ and other factors have
been taken into account.

If __mutableattributes__ is defined as a sequence of strings, these
attributes will not be shared between superclasses and their
subclasses.  E.g., if you have a class variable that contains a list
and you append to that list, changes to subclasses will effect
superclasses unless you add the attribute here.

Also defines classinstancemethod, which acts as either a class method
or an instance method depending on where it is called.

import copy
from . import events
from sqlobject.compat import with_metaclass

import itertools
counter = itertools.count()

__all__ = ('classinstancemethod', 'DeclarativeMeta', 'Declarative')

[docs]class classinstancemethod(object): """ Acts like a class method when called from a class, like an instance method when called by an instance. The method should take two arguments, 'self' and 'cls'; one of these will be None depending on how the method was called. """ def __init__(self, func): self.func = func def __get__(self, obj, type=None): return _methodwrapper(self.func, obj=obj, type=type)
class _methodwrapper(object): def __init__(self, func, obj, type): self.func = func self.obj = obj self.type = type def __call__(self, *args, **kw): assert 'self' not in kw and 'cls' not in kw, ( "You cannot use 'self' or 'cls' arguments to a " "classinstancemethod") return self.func(*((self.obj, self.type) + args), **kw) def __repr__(self): if self.obj is None: return ('<bound class method %s.%s>' % (self.type.__name__, self.func.__name__)) else: return ('<bound method %s.%s of %r>' % (self.type.__name__, self.func.__name__, self.obj))
[docs]class DeclarativeMeta(type): def __new__(meta, class_name, bases, new_attrs): post_funcs = [] early_funcs = [] events.send(events.ClassCreateSignal, bases[0], class_name, bases, new_attrs, post_funcs, early_funcs) cls = type.__new__(meta, class_name, bases, new_attrs) for func in early_funcs: func(cls) if '__classinit__' in new_attrs: if hasattr(cls.__classinit__, '__func__'): cls.__classinit__ = staticmethod(cls.__classinit__.__func__) else: cls.__classinit__ = staticmethod(cls.__classinit__) cls.__classinit__(cls, new_attrs) for func in post_funcs: func(cls) return cls
[docs]class Declarative(with_metaclass(DeclarativeMeta, object)): __unpackargs__ = () __mutableattributes__ = () __restrict_attributes__ = None def __classinit__(cls, new_attrs): cls.declarative_count = next(counter) for name in cls.__mutableattributes__: if name not in new_attrs: setattr(cls, copy.copy(getattr(cls, name))) def __instanceinit__(self, new_attrs): if self.__restrict_attributes__ is not None: for name in new_attrs: if name not in self.__restrict_attributes__: raise TypeError( '%s() got an unexpected keyword argument %r' % (self.__class__.__name__, name)) for name, value in new_attrs.items(): setattr(self, name, value) if 'declarative_count' not in new_attrs: self.declarative_count = next(counter) def __init__(self, *args, **kw): if self.__unpackargs__ and self.__unpackargs__[0] == '*': assert len(self.__unpackargs__) == 2, \ "When using __unpackargs__ = ('*', varname), " \ "you must only provide a single variable name " \ "(you gave %r)" % self.__unpackargs__ name = self.__unpackargs__[1] if name in kw: raise TypeError( "keyword parameter '%s' was given by position and name" % name) kw[name] = args else: if len(args) > len(self.__unpackargs__): raise TypeError( '%s() takes at most %i arguments (%i given)' % (self.__class__.__name__, len(self.__unpackargs__), len(args))) for name, arg in zip(self.__unpackargs__, args): if name in kw: raise TypeError( "keyword parameter '%s' was given by position and name" % name) kw[name] = arg if '__alsocopy' in kw: for name, value in kw['__alsocopy'].items(): if name not in kw: if name in self.__mutableattributes__: value = copy.copy(value) kw[name] = value del kw['__alsocopy'] self.__instanceinit__(kw) def __call__(self, *args, **kw): kw['__alsocopy'] = self.__dict__ return self.__class__(*args, **kw)
[docs] @classinstancemethod def singleton(self, cls): if self: return self name = '_%s__singleton' % cls.__name__ if not hasattr(cls, name): setattr(cls, name, cls(declarative_count=cls.declarative_count)) return getattr(cls, name)
@classinstancemethod def __repr__(self, cls): if self: name = '%s object' % self.__class__.__name__ v = self.__dict__.copy() else: name = '%s class' % cls.__name__ v = cls.__dict__.copy() if 'declarative_count' in v: name = '%s %i' % (name, v['declarative_count']) del v['declarative_count'] # @@: simplifying repr: # v = {} names = v.keys() args = [] for n in self._repr_vars(names): args.append('%s=%r' % (n, v[n])) if not args: return '<%s>' % name else: return '<%s %s>' % (name, ' '.join(args)) @staticmethod def _repr_vars(dictNames): names = [n for n in dictNames if not n.startswith('_') and n != 'declarative_count'] names.sort() return names
def setup_attributes(cls, new_attrs): for name, value in new_attrs.items(): if hasattr(value, '__addtoclass__'): value.__addtoclass__(cls, name)