问题

我在models.py中有两个模型

```python
class Teams(models.Model):
    Name = models.CharField(verbose_name="Team Name", max_length=200)
    Slug = AutoSlugField(populate_from="Name", always_update=True, editable=True, verbose_name="Team Slug")
    Location = models.CharField(verbose_name="Team Location", max_length=200)
    Leader = models.ForeignKey('Members', on_delete=models.SET_NULL, null=True, blank=True)
    ArrivalDate = models.DateTimeField(default=timezone.now, editable=False, verbose_name="Arrival Date")
    DepartureDate = models.DateTimeField(null=True, blank=True, verbose_name="Departure Date")

和

class Members(models.Model):
    Name = models.CharField(verbose_name="Member Name", max_length=200)
    Team = models.ForeignKey(Teams, on_delete=models.CASCADE)
    PhoneNumber = models.CharField(max_length=20, null=True, blank=True)
    Email = models.EmailField(max_length=50, null=True, blank=True)
    BloodType = models.CharField(max_length=3, choices=BLOOD_TYPE_CHOICES, null=True, blank=True)
    isLeader = models.BooleanField(default=False)

当Members模型中的isLeader字段设置为True时，我想要更新Teams模型中的Leader字段。

提前感谢

<details>
<summary>英文:</summary>

I have to models in models.py

class Teams(models.Model):
Name = models.CharField(verbose_name="Team Name", max_length=200)
Slug = AutoSlugField(populate_from="Name", always_update=True, editable=True, verbose_name="Team Slug")
Location = models.CharField(verbose_name="Team Location", max_length=200)
Leader = models.ForeignKey('Members', on_delete=models.SET_NULL, null=True, blank=True)
ArrivalDate = models.DateTimeField(default=timezone.now, editable=False, verbose_name="Arrival Date")
DepartureDate = models.DateTimeField(null=True, blank=True, verbose_name="Departure Date")

and

class Members(models.Model):
Name = models.CharField(verbose_name="Member Name", max_length=200)
Team = models.ForeignKey(Teams, on_delete=models.CASCADE)
PhoneNumber = models.CharField(max_length=20, null=True, blank=True)
Email = models.EmailField(max_length=50, null=True, blank=True)
BloodType = models.CharField(max_length=3, choices=BLOOD_TYPE_CHOICES, null=True, blank=True)
isLeader = models.BooleanField(default=False)

When isLeader field in Members field set True, I want to update Leader field in Teams model.



Thanks in advance

</details>


# 答案1
**得分**: 1

最好的方法是根本不存储领导者，因为那是重复的数据。您可以使用以下方法确定领导者。否则，您将存储重复的数据，正如您自己已经发现的那样，保持表同步实际上是一个比人们可能期望的要困难得多的问题：

```python
class Team(models.Model):
    name = models.CharField(verbose_name='Team Name', max_length=200)
    slug = AutoSlugField(
        populate_from='Name',
        always_update=True,
        editable=True,
        verbose_name='Team Slug',
    )
    location = models.CharField(verbose_name='Team Location', max_length=200)
    arrival_date = models.DateTimeField(
        default=timezone.now, editable=False, verbose_name='Arrival Date'
    )
    departure_date = models.DateTimeField(
        null=True, blank=True, verbose_name='Departure Date'
    )

    @property
    def leader(self):
        return Member.objects.filter(team=self, is_leader=True).first()

在Member模型中，我们可以添加一个约束，确保每个团队最多只有一个领导者：

from django.db.models import Q

class Member(models.Model):
    name = models.CharField(verbose_name='Member Name', max_length=200)
    team = models.ForeignKey(Team, on_delete=models.CASCADE)
    phone_number = models.CharField(max_length=20, null=True, blank=True)
    email = models.EmailField(max_length=50, null=True, blank=True)
    blood_type = models.CharField(
        max_length=3, choices=BLOOD_TYPE_CHOICES, null=True, blank=True
    )
    is_leader = models.BooleanField(default=False)

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=('team',),
                condition=Q(is_leader=True),
                name='one_leader_per_team'
            ),
        ]

注意: 通常情况下，当相关字段发生更改时，不应更改slug。正如在文章Cool URIs don't change中所写的那样，URI不应更改，因为这些可以被收藏夹保存。因此，slug应该仅在创建对象时创建，而不是在更改slug依赖的任何字段时创建。

注意: 通常情况下，Django模型的名称应该是单数形式，因此应该是Member而不是Members。

注意: 通常情况下，Django模型中字段的名称以蛇形命名法书写，而不是帕斯卡命名法，因此应该是：blood_type而不是Bloodtype。

@property
def <b>leader</b>(self):
    return Member.objects.filter(team=self, is_leader=True).first()</code></pre>

class Meta:
    constraints = [
        models.UniqueConstraint(
            fields=('team',),
            condition=Q(is_leader=True),
            name='one_leader_per_team'
        ),
    ]</code></pre>