django orm 管理器 objects

Posted 2020-10-13 Hu知非

给某张表的管理器重命名

class User(models.Model):
        name = models.CharField(max_length=100)
        people = models.Manager()
        
    获取所有的queryset，用people替代objects
    obj = model.User.people.all()

 

重写管理器，增加或覆盖某些功能

class MyManager(models.Manager):
        def with_counts(self):
            from django.db import connection
            cursor = connection.cursor()
            cursor.execute("select name,count(1) from user group by name")
            result_list = []
            for row in cursor.fetchall():
                p = self.model(name=row[0])
                p.count = row[1]
                result_list.append(p)
            return result_list
    
    class User(models.Model):
        name = models.CharField(max_length=100)
        sex = models.CharField(max_length=100)
        objects = MyManager()
        
        class Meta:
            db_table = ‘user‘
            
    #查询
    obj = models.User.objects.with_counts()
    print obj[0].count  # 1

 

重写manager.get_queryset()覆盖管理器自带的Queryset

get_queryset()会根据需要返回查询集

#增加一个只查询男性用户的管理器
    class MaleUserManager(models.Model):
        def get_queryset(self):
            return super(MaleUserManager,self).get_queryset().filter(sex=‘male‘)
        
    class User(models.Model):
        name = models.CharField(max_length=100)
        sex = models.CharField(max_length=100)
        objects = models.Manager()
        male_objects = MaleUserManager()
        
        class Meta:
            db_table = ‘user‘
    
    
    #查询
    可以使用 User.objects.all(),User.male_objects.all()