Make a function be a new member of an instance object

bind_function_to_instance.py

# create the tables

db.define_table('person',
    Field('name'),
    Field('gender'),
    Field('birthdate', 'date'))

db.define_table('animal',
    Field('name'),
    Field('gender'),
    Field('birthdate', 'date'))


# Bind the function to tables.
# Note the use of "self".
# Due to this decorator, we're "inside" the instance.

@make_member_of(db.person, 'just_men')
@make_member_of(db.animal, 'just_males')
def get_just_gender_equals_m(self):
    return self._db(self.gender == 'm').select()


# Use the function as a regular table method.
db.person.just_men()
db.animal.just_males()

make_member_of.py

# Create the decorator function

def make_member_of(instance, method_name=None):
    def _decorated(f):
        import types
        f2 = types.MethodType(f, instance, instance.__class__)
	_name = method_name or f.func_name
        setattr(instance, _name, f2)
        return f
    return _decorated

# note: this must be defined before binding functions to instance.