Django 知识库：Manager()自定义模型方法

class Book(models.Model):
    title = models.CharField(max_length=100)

    def save(self, *args, **kwargs):
        # 在这里执行自定义逻辑
        ...

        super().save(*args, **kwargs)

class Book(models.Model):
    title = models.CharField(max_length=100)

    @classmethod
    def create(cls, title):
        book = cls(title=title)
        # do something with the book
        return book

book = Book.create('Foo')
book.save()

class BookManager(models.Manager):
    def create_book(self, title):
        book = self.create(title=title)
        # do something with the book
        book.save()
        return book


class Book(models.Model):
    title = models.CharField(max_length=100)

    objects = models.Manager() # 默认管理器
    custom = BookManager() # 自定义管理器

Obj.objects.create()  # 中间那个 objects 就是友情赠送的默认管理器

book = Book.custom.create_book('Bar')

class BookManager(models.Manager):
    def get_queryset(self):
        return super().get_queryset().filter(title__contains='money')


class Book(models.Model):
    title = models.CharField(max_length=100)

    objects = models.Manager()
    custom = BookManager()

class PollManager(models.Manager):
    def with_counts(self):
        from django.db import connection
        with connection.cursor() as cursor:
            cursor.execute("""
                SELECT p.id, p.question, p.poll_date, COUNT(*)
                FROM polls_opinionpoll p, polls_response r
                WHERE p.id = r.poll_id
                GROUP BY p.id, p.question, p.poll_date
                ORDER BY p.poll_date DESC""")
            result_list = []
            for row in cursor.fetchall():
                p = self.model(id=row[0], question=row[1], poll_date=row[2])
                p.num_responses = row[3]
                result_list.append(p)
        return result_list

class OpinionPoll(models.Model):
    question = models.CharField(max_length=200)
    poll_date = models.DateField()
    objects = PollManager()

class Response(models.Model):
    poll = models.ForeignKey(OpinionPoll, on_delete=models.CASCADE)
    person_name = models.CharField(max_length=50)
    response = models.TextField()