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Viewing changes to django/db/models/fields/subclassing.py

  • Committer: Bazaar Package Importer
  • Author(s): Chris Lamb
  • Date: 2010-05-21 07:52:55 UTC
  • mfrom: (1.3.6 upstream)
  • mto: This revision was merged to the branch mainline in revision 28.
  • Revision ID: james.westby@ubuntu.com-20100521075255-ii78v1dyfmyu3uzx
Tags: upstream-1.2
Import upstream version 1.2

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django/db/models/fields/subclassing.py
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"""
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Convenience routines for creating non-trivial Field subclasses.
 
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Convenience routines for creating non-trivial Field subclasses, as well as
 
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backwards compatibility utilities.
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Add SubfieldBase as the __metaclass__ for your Field subclass, implement
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to_python() and the other necessary methods and everything will work seamlessly.
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"""
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class SubfieldBase(type):
 
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from inspect import getargspec
 
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from warnings import warn
 
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def call_with_connection(func):
 
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    arg_names, varargs, varkwargs, defaults = getargspec(func)
 
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    updated = ('connection' in arg_names or varkwargs)
 
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    if not updated:
 
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        warn("A Field class whose %s method hasn't been updated to take a "
 
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            "`connection` argument." % func.__name__,
 
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            PendingDeprecationWarning, stacklevel=2)
 
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    def inner(*args, **kwargs):
 
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        if 'connection' not in kwargs:
 
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            from django.db import connection
 
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            kwargs['connection'] = connection
 
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            warn("%s has been called without providing a connection argument. " %
 
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                func.__name__, PendingDeprecationWarning,
 
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                stacklevel=1)
 
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        if updated:
 
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            return func(*args, **kwargs)
 
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        if 'connection' in kwargs:
 
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            del kwargs['connection']
 
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        return func(*args, **kwargs)
 
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    return inner
 
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def call_with_connection_and_prepared(func):
 
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    arg_names, varargs, varkwargs, defaults = getargspec(func)
 
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    updated = (
 
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        ('connection' in arg_names or varkwargs) and
 
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        ('prepared' in arg_names or varkwargs)
 
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    )
 
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    if not updated:
 
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        warn("A Field class whose %s method hasn't been updated to take "
 
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            "`connection` and `prepared` arguments." % func.__name__,
 
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            PendingDeprecationWarning, stacklevel=2)
 
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    def inner(*args, **kwargs):
 
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        if 'connection' not in kwargs:
 
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            from django.db import connection
 
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            kwargs['connection'] = connection
 
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            warn("%s has been called without providing a connection argument. " %
 
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                func.__name__, PendingDeprecationWarning,
 
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                stacklevel=1)
 
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        if updated:
 
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            return func(*args, **kwargs)
 
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        if 'connection' in kwargs:
 
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            del kwargs['connection']
 
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        if 'prepared' in kwargs:
 
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            del kwargs['prepared']
 
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        return func(*args, **kwargs)
 
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    return inner
 
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class LegacyConnection(type):
 
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    """
 
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    A metaclass to normalize arguments give to the get_db_prep_* and db_type
 
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    methods on fields.
 
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    """
 
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    def __new__(cls, names, bases, attrs):
 
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        new_cls = super(LegacyConnection, cls).__new__(cls, names, bases, attrs)
 
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        for attr in ('db_type', 'get_db_prep_save'):
 
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            setattr(new_cls, attr, call_with_connection(getattr(new_cls, attr)))
 
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        for attr in ('get_db_prep_lookup', 'get_db_prep_value'):
 
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            setattr(new_cls, attr, call_with_connection_and_prepared(getattr(new_cls, attr)))
 
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        return new_cls
 
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class SubfieldBase(LegacyConnection):
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    """
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    A metaclass for custom Field subclasses. This ensures the model's attribute
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    has the descriptor protocol attached to it.
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    def __get__(self, obj, type=None):
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        if obj is None:
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            raise AttributeError('Can only be accessed via an instance.')
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        return obj.__dict__[self.field.name]        
 
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        return obj.__dict__[self.field.name]
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    def __set__(self, obj, value):
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        obj.__dict__[self.field.name] = self.field.to_python(value)