Loops Django的倍数

Question

我有以下两种型号的ASPBoookings和运动员。运动员模型通过名为运动员的外键连接到ASPBookings模型。

我正在尝试创建一个循环，该循环将遍历ASPBooking表中的所有预订，并找出哪个是每个运动员的最新预订(该表可以包含对相同或不同运动员(athlete_id)的多个预订)。

一旦我有了这个信息(booking_date和athlete_id)，我就想要自动更新运动员模型中的“最新的ASP会话字段”。

到目前为止，这就是我所尝试的。我可以循环浏览ASPBookings表中的预订，并使用booking_date和athlete_id检索和更新“最新的ASP会话字段”，但是对于表中的多个不同的运动员，我不能这样做。当前，视图只标识最新的预订和指定的athlete_id，然后更新字段。

提前感谢您的帮助。

以下是代码：

ASPBookings模型

class ASPBookings(models.Model):
    asp_booking_ref = models.CharField(max_length=10, default=1)
    program_type = models.CharField(max_length=120, default='asp')
    booking_date = models.DateField()
    booking_time = models.CharField(max_length=10, choices=booking_times)
    duration = models.CharField(max_length=10, choices=durations, default='0.5')
    street = models.CharField(max_length=120)
    suburb = models.CharField(max_length=120)
    region = models.CharField(max_length=120, choices=regions, default='Metro')
    post_code = models.CharField(max_length=40)
    organisation_type = models.CharField(max_length=120,choices=organisation_types, default='Government School')
    audience_number = models.CharField(max_length=10)
    presentation_form = models.CharField(max_length=120, choices=presentation_form_options, default='Face to Face')
    contact_name = models.CharField(max_length=80)
    email = models.EmailField()
    phone_number = models.CharField(max_length=120)
    comments = models.TextField()
    status = models.CharField(max_length=80, choices=statuses, default='TBC')
    email_sent = models.BooleanField(default=False)
    athlete = models.ForeignKey(Athlete, default= '1', on_delete=models.CASCADE)

    def __str__(self):
        return self.contact_name
        
    # return URL after the POST has been submitted.
    def get_absolute_url(self):
        return reverse('vistours:success')

运动员模型

class Athlete(models.Model):
    athlete_ref = models.CharField(max_length=10, default=1)
    athlete_name = models.CharField(max_length=80)
    email = models.EmailField()
    phone_number = models.CharField(max_length=120)
    home = models.CharField(max_length=120)
    education = models.CharField(max_length=120)
    sport = models.CharField(max_length=120, choices=sports, default='1500m Runner')
    notes = models.TextField(default='None')
    gender = models.CharField(max_length=120, choices=genders, default='Not Specified')
    para_athlete = models.BooleanField(blank=True)
    working_with_children = models.BooleanField(blank=True)
    expiry_date = models.DateField(blank=True, null=True)
    available = models.BooleanField(blank=True)
    available_from = models.DateField(blank=True, null=True)
    bfbw = models.BooleanField(blank=True)
    latest_bfbw_session = models.DateField(blank=True, null=True)
    number_bfbw_sessions = models.CharField(blank=True, null=True, max_length=10)
    asp = models.BooleanField(blank=True)
    latest_asp_session = models.DateField(blank=True, null=True)
    number_asp_sessions = models.CharField(blank=True, null=True, max_length=10)
    tours = models.BooleanField(blank=True)
    latest_tours_session = models.DateField(blank=True, null=True)
    number_tours_sessions = models.CharField(blank=True, null=True, max_length=10)

    def __str__(self):
        return self.athlete_name

    # return URL after the POST has been submitted.
    def get_absolute_url(self):
        return reverse('home')

视图

# Complete first loop for inital values.
    for date in asp_data:
        if date.booking_date != None:
            first_loop = date.booking_date
            athl_id = date.athlete_id
            break
    # If next value is greater than inital value, replace current values.      
    for date in asp_data:
        if date.booking_date != None:
            if date.booking_date > first_loop:
                first_loop = date.booking_date
                athl_id = date.athlete_id
    

    print(first_loop)
    print(athl_id)

    update_date = Athlete.objects.get(id=athl_id)
    update_date.latest_asp_session = first_loop
    update_date.save()

Answer 1

不需要循环。您只需一次就可以为所有运动员做到这一点，使用子查询将所有繁重工作留给您的数据库：

from django.db.models import F, OuterRef, Subquery

bookings = ASPBookings.objects.filter(
    athlete=OuterRef('pk')
).order_by('-booking_date')

Athlete.objects.annotate(
    latest_asp_booking_date=Subquery(
        bookings.values('booking_date')[:1]
    )
).update(
    latest_asp_session=F('latest_asp_booking_date')
)