如何使用来自第二个模型的复杂数据对我的 Django 模型进行排序？

Question

我有 3 个 django 模型（本示例已简化）：

class Fighter (models.Model):
    name = models.CharField(max_length=100)
    weight_class = models.ForeignKey(WeightClass, related_name="fighter_weight_class")

class Bout (models.Model):
    fighter_1 = models.ForeignKey(Fighter, related_name="bout_fighter_1")
    fighter_2 = models.ForeignKey(Fighter, related_name="bout_fighter_2")
    winner = models.ForeignKey(Fighter, related_name="bout_winner", blank=True, 
        null=True, help_text='Leave blank for draw.') 
    date = models.DateField()
    cancelled = models.BooleanField()

class WeightClass (models.Model):
    name = models.CharField(max_length=100)

我希望能够按他们的统计数据列出战士。我创造了这些 函数（有效）来计算他们的胜负和平局：

def get_bouts_with_fighter (fighter):
 return Bout.objects.filter(fighter_1 = fighter) | \
  Bout.objects.filter(fighter_2 = fighter) 

def get_fighter_wins (fighter):
 return Bout.objects.filter(winner=fighter)

def get_bouts_fought_not_won (fighter):
 return get_bouts_with_fighter(fighter) \
  .exclude(cancelled=True) \
     .exclude(date__gt = datetime.datetime.now())

def get_fighter_losses (fighter):
 return get_bouts_fought_not_won(fighter)\
  .exclude(winner=fighter)\
  .exclude(winner=None)

def get_fighter_draws (fighter):
 return get_bouts_fought_not_won(fighter)\
  .filter(winner=None)

但是现在，在对视图的输出进行排序时，我遇到了两个问题：

1. “排序”既不正确也不一致。
2. 在排序过程中，我失去了战士的名字

这里是当前代码（如果不进行排序则输出正确）：

def list(request, sort=None):

    class WeightGroup:
        """
        Internal class to keep data organized by weight class.
        """
        weight_class = None
        fighters = None

        def win_sort (self):
            wins = []
            winners = []

            for fighter in self.fighters:
                wins.append((fighter.id, get_fighter_wins(fighter)),)
            for win in (sorted(wins, key=lambda f: f[1], reverse=True)):
                winners.append(Fighter.objects.filter(id=win[0])) #build winner list by score

            self.fighters = winners

        def loss_sort (self):
            #TO DO:
            pass

        def draw_sort (self):
            #TO DO:
            pass


    title = 'Fighters'
    weight_groups = []

    for weight_class in WeightClass.objects.all():
        weight_group = WeightGroup()
        weight_group.weight_class = weight_class
        weight_group.fighters = Fighter.objects.filter(weight_class=weight_class)
        weight_groups.append(weight_group) 

    if sort in ['wins', 'losses', 'draws']:
        title += ', sorted by ' + sort
        for weight_group in weight_groups:
            if (sort == 'wins'): weight_group.win_sort()
            if (sort == 'losses'): weight_group.loss_sort()
            if (sort == 'draws'): weight_group.draw_sort()

    return render_to_response ('fighters/list.html',{
        'title': title, 
        'weight_groups':weight_groups
    })

任何关于我如何使它工作的建议将不胜感激！

Answer 1

我已经设法解决了这两个问题：

1. 我添加的是胜利集合，而不是该列表的“长度”。 我需要改变这个：

   wins.append((fighter.id, get_fighter_wins(fighter)),)

   到：

   wins.append((fighter.id, len(get_fighter_wins(fighter))),)

2. 我正在构建一个查询集列表，而不是一个对象列表。 我需要改变这个：

   winners.append(Fighter.objects.filter(id=win[0]))

   到：

   winners.append(Fighter.objects.get(id=win[0]))

（向我的朋友 Attila 干杯，他向我解释了第二个问题。）

顺便说一句，我的最终代码没有使用三个单独的函数。相反，我这样做了：

    .
    .
    .

class WeightGroup:
    .
    .
    .
            def sort (self, sort_function):
                scores = []
                scorers = []

                for fighter in self.fighters:
                    scores.append((fighter.id, len(sort_function(fighter))),)
                for score in (sorted(scores, key=lambda f: f[1], reverse=True)):
                    scorers.append(Fighter.objects.get(id=score[0])) 

                self.fighters = scorers
    .
    .
    .
        if sort in ['wins', 'losses', 'draws']:
            title += ', sorted by ' + sort
            for weight_group in weight_groups:
                if (sort == 'wins'): weight_group.sort(get_fighter_wins)
                if (sort == 'losses'): weight_group.sort(get_fighter_losses)
                if (sort == 'draws'): weight_group.sort(get_fighter_draws)
    .
    .
    .