问在Django中创建自定义字段查找

EN

from django.db.models import Lookup

class AbsoluteValueLessThan(Lookup):
    lookup_name = 'lt'

    def as_sql(self, qn, connection):
        lhs, lhs_params = qn.compile(self.lhs.lhs)
        rhs, rhs_params = self.process_rhs(qn, connection)
        params = lhs_params + rhs_params + lhs_params + rhs_params
        return '%s < %s AND %s > -%s' % (lhs, rhs, lhs, rhs), params

AbsoluteValue.register_lookup(AbsoluteValueLessThan)

class PersonQuerySet(models.query.QuerySet):
    def in_age_range(self, min, max):
        return self.filter(age__gte=min, age__lt=max)

class PersonManager(models.Manager):
    def get_query_set(self):
         return PersonQuerySet(self.model)

    def __getattr__(self, name):
        return getattr(self.get_query_set(), name)

class Person(models.Model):
    age = #...

    objects = PersonManager()

Person.objects.in_age_range(20,30)

Person.objects.exclude(somefield = some_value).in_age_range(20, 30)

class PersonManger(models.Manager):
    def in_age_range(self, min, max):
        return self.filter(age__gte=min, age__lt=max)

class Person(models.Model):
    age = #...

    objects = PersonManager()

twentysomethings = Person.objects.in_age_range(20, 30)