app/django/db/models/fields/subclassing.py
author Lennard de Rijk <ljvderijk@gmail.com>
Mon, 16 Feb 2009 20:38:35 +0000
changeset 1364 b2709805fafe
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Update org bulk accept script. The script now: 1) leaves correctly control to the browser to update the GUI of the progress bar during ajax communication. 2) Displays an error if something went wrong (I've tried in my box stopping the server while doing the requests), and show a retry button to fetch again the list of the applications that are still not accepted and iterate over them again (seems to recover correctly restarting the server after the error in my box) 3) doesn't display any text at the beginning, and the button has the correct CSS class assigned 4) Check if there are applications to accept, if not displays a message stating that there are no orgs to accept. Patch by: Mario Ferraro Reviewed by: Lennard de Rijk

"""
Convenience routines for creating non-trivial Field subclasses.

Add SubfieldBase as the __metaclass__ for your Field subclass, implement
to_python() and the other necessary methods and everything will work seamlessly.
"""

class SubfieldBase(type):
    """
    A metaclass for custom Field subclasses. This ensures the model's attribute
    has the descriptor protocol attached to it.
    """
    def __new__(cls, base, name, attrs):
        new_class = super(SubfieldBase, cls).__new__(cls, base, name, attrs)
        new_class.contribute_to_class = make_contrib(
                attrs.get('contribute_to_class'))
        return new_class

class Creator(object):
    """
    A placeholder class that provides a way to set the attribute on the model.
    """
    def __init__(self, field):
        self.field = field

    def __get__(self, obj, type=None):
        if obj is None:
            raise AttributeError('Can only be accessed via an instance.')
        return obj.__dict__[self.field.name]        

    def __set__(self, obj, value):
        obj.__dict__[self.field.name] = self.field.to_python(value)

def make_contrib(func=None):
    """
    Returns a suitable contribute_to_class() method for the Field subclass.

    If 'func' is passed in, it is the existing contribute_to_class() method on
    the subclass and it is called before anything else. It is assumed in this
    case that the existing contribute_to_class() calls all the necessary
    superclass methods.
    """
    def contribute_to_class(self, cls, name):
        if func:
            func(self, cls, name)
        else:
            super(self.__class__, self).contribute_to_class(cls, name)
        setattr(cls, self.name, Creator(self))

    return contribute_to_class