Question

根据Django docs，我创建了人与博物馆申请日期之间的关系。

首先是模型（删除了不必要的字段）：

class Agent(models.Model):
    name = models.CharField(max_length=255)
    dates = models.ManyToManyField(HistoricDate, 'date_for_agent', models.CASCADE, through='AgentDateType')
    . . . .

class HistoricDate(models.Model):
    display = models.CharField(max_length=255, help_text='Textual representation of date')
    earliest = models.CharField(max_length=15, blank=True)
    earliest_accuracy = models.BooleanField(default=False, verbose_name="circa")
    latest = models.CharField(max_length=15, blank=True)
    latest_accuracy = models.BooleanField(default=False, verbose_name="circa")

class AgentDateType(models.Model):
    datation = models.ForeignKey(HistoricDate, models.PROTECT)
    dated = models.ForeignKey(Agent, models.CASCADE)
    date_type = models.CharField(max_length=31, choices=date_types)
    . . . .

然后测试：

caesar = Agent.objects.create(name="Gaius Julius Caesar", name_type="personal", culture="Ancient Rome", display="Julius Caesar (Roman, 100–44 B.C.)")
c_life = HistoricDate.objects.create(display="13 July 100–15 March 44 B.C.", earliest="-100-07-13", earliest_accuracy=False, latest="-44-03-15", latest_accuracy=False)
c_act = HistoricDate.objects.create(display="60–44 B.C.", earliest="-60", earliest_accuracy=False, latest="-44-03-15", latest_accuracy=False)

caesar_lives = AgentDateType.objects.create(dated=caesar, datation=c_life, source="Suetonius, Lives of the Caesars", date_type="life")
caesar_acts = AgentDateType.objects.create(dated=caesar, datation=c_act, source="Livy", date_type="activity")

现在，以下查询返回预期的集合：

AgentDateType.objects.all()
c_life.date_for_agent.all()
c_act.date_for_agent.all()

但是，caesar.dates.all()应该是最简单的，返回一个空集。是什么给了什么？

Answer 1

Django＆＃39; ManyToManyField采取不符合您提供的顺序的位置参数。请参阅source for M2M。我建议你使用关键字参数，因为位置参数可能导致问题，更不用说在次要版本之间进行更改。

Django多对多查询all（）返回空集

1 个答案: