Django REST按日期序列化字段组

Question

问题：无法按日期对 JSON 输出进行分组

本文底部的解决方案

我正在序列化一个模型并得到这个输出：

[
    {
        "date": "2020-11-24",
        "name": "Chest",
        "workout": {
            "name": "Chest",
            "exercise": 1,
            "repetitions": 10,
            "weight": 80
        }
    },
    {
        "date": "2020-11-24",
        "name": "Chest",
        "workout": {
            "name": "Chest",
            "exercise": 1,
            "repetitions": 10,
            "weight": 85
        }
    },
    {
        "date": "2020-11-24",
        "name": "Chest",
        "workout": {
            "name": "Chest",
            "exercise": 1,
            "repetitions": 10,
            "weight": 90
        }
    },

我想像下面的 JSON 一样获取它，并按 date 对其进行分组。

[
    {
        "date": "2020-11-24",
        "workout": {
            "name": "Chest",
            "exercise": 1,
            "repetitions": 10,
            "weight": 80
        },
            "name": "Chest",
            "exercise": 1,
            "repetitions": 10,
            "weight": 85
        },
            "name": "Chest",
            "exercise": 1,
            "repetitions": 10,
            "weight": 90
        },
    }
]

我有一个模型：

class WorkoutLog(models.Model):
    date = models.DateField()
    name = models.CharField(max_length=50) #When save() name = Workout.name
    exercise = models.ForeignKey('Exercise', related_name='log', on_delete=models.CASCADE)
    repetitions = models.IntegerField()
    weight = models.IntegerField()

尝试按日期对 JSON 进行序列化和分组：

class WorkoutLogSerializer(serializers.ModelSerializer):
    class Meta:
        model = WorkoutLog
        fields = ['date', 'workout']
    
    workout = serializers.SerializerMethodField('get_workout')

    def get_workout(self, obj):
        return {
            'name': obj.name,
            'exercise': obj.exercise_id,
            'repetitions': obj.repetitions,
            'weight': obj.weight,
        }

代码让我可以自定义字段布局，但不能真正按日期对其进行分组。您对如何构建它有什么建议吗？

非常感谢大家的帮助！

如果需要，这是我的 view.py

def workout_log(request):
    if request.method == 'GET':
        workout_log = WorkoutLog.objects.all()
        serializer = WorkoutLogSerializer(workout_log, many=True)
        return JsonResponse(serializer.data, safe=False)

Mahmoud Adel 的解决方案：

views.py

def workout_log(request):
    if request.method == 'GET':
        workout_log = WorkoutLog.objects.order_by('date').values('date').distinct()
        serializer = WorkoutLogSerializer(workout_log, many=True)
        return JsonResponse(serializer.data, safe=False)

序列化器.py

class WorkoutFieldSerializer(serializers.Serializer):
      name = serializers.CharField()
      #exercise = serializers.IntegerField()
      repetitions = serializers.IntegerField()
      weight = serializers.IntegerField()
      
class WorkoutLogSerializer(serializers.ModelSerializer):
    class Meta:
        model = WorkoutLog
        fields = ['date', 'workout']
    
    workout = serializers.SerializerMethodField('get_workout')

    def get_workout(self, obj):
        workouts = WorkoutLog.objects.filter(date=obj['date'])
        workout_serializer = WorkoutFieldSerializer(workouts, many=True)
        return workout_serializer.data

Answer 1

你可以这样做

让我们先从你的观点开始，我会像这样调整查询集

def workout_log(request):
    if request.method == 'GET':
        workout_log = WorkoutLog.objects.order_by('date').distinct('date').only('date')
        serializer = WorkoutLogSerializer(workout_log, many=True)
        return JsonResponse(serializer.data, safe=False)

然后在你的WorkoutLogSerializer

class WorkoutLogSerializer(serializers.ModelSerializer):
    class Meta:
        model = WorkoutLog
        fields = ['date', 'workout']
    
    workout = serializers.SerializerMethodField('get_workout')

    def get_workout(self, obj):
        workouts = WorkoutLog.objects.filter(date=obj.date)
        workout_serializer = WorkoutSerializer(workouts, many=True)
        return workout_serializer.data

最后，创建WorkoutSerializer

class WorkoutSerializer(serializers.Serializers):
      name = serializers.CharField()
      exercise = serializers.IntegerField()
      repetitions = serializers.IntegerField()
      weight = serializers.IntegerField()

之前的方法会先到数据库获取distinct的日期，然后WorkoutLogSerializer会使用每个日期来选择对应的拥有它的对象，然后我们序列化这些对象。

我们这样做会得到预期的结果，请注意这将在2 DB hits 中导致，可能还有另一种方法可以在一次数据库命中中做到这一点，如果我会更新我的答案想通了

注意：我写这篇文章是为了解释我没有运行它的流程和逻辑，虽然它应该可以工作，但我可能会忘记一些会显示错误的内容，请随意尝试它。

更新：如果您使用 SQLite，请检查此答案 cmets。