Question

我正在添加“已添加”字段以检查添加了用户的帖子（装备）的类别。这听起来很糟糕，所以让我们深入研究代码。

我想优化get_categories（self，obj）函数。

class CategorySerializer(serializers.ModelSerializer):
    added = serializers.BooleanField()
    class Meta:
        model = Category
        fields = (
            'id',
            'name',
            'added'
        )


class OutfitDetailSerializer(serializers.ModelSerializer):

    def get_categories(self, obj):
        user = self.context['request'].user
        categories = Category.objects.filter(owner=user)
        added = categories.extra(select={'added': '1'}).filter(outfits__pk=obj.pk)
        added = list(added.values('added', 'name', 'id'))
        added_f = categories.extra(select={'added': '0'}).exclude(outfits__pk=obj.pk)
        added_f = list(added_f.values('added', 'name', 'id'))
        categories = added + added_f
        return CategorySerializer(categories, many=True).data

输出低于！

"categories": [{
        "id": 1,
        "name": "Gym",
        "added": true
    }, {
        "id": 2,
        "name": "School",
        "added": false
    }, {
        "id": 3,
        "name": "hollymo",
        "added": true
    }, {
        "id": 4,
        "name": "Normal",
        "added": false
    }, {
        "id": 6,
        "name": "New Category",
        "added": false
    }
]

这是models.py

class Outfit(models.Model):
    ...
    user = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True)
    content = models.CharField(max_length=30)
    ...

class Category(models.Model):
    name = models.CharField(max_length=20)
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True)
    outfits = models.ManyToManyField(Outfit, related_name="categories", blank=True)
    main_img = models.ImageField(
                            upload_to=upload_location_category,
                            null=True,
                            blank=True)
    ...

这里是repo for test

Answer 1

如果我说得对，您可以使用django raw sql获取必要的数据：

q = """\
SELECT yourappname_category.id,
       yourappname_category.name,
       COUNT(outfit_id) > 0 as added 
FROM yourappname_category
  LEFT JOIN yourappname_category_outfits 
      ON yourappname_category.id = yourappname_category_outfits.category_id 
         AND yourappname_category_outfits.outfit_id=%s
WHERE yourappname_category.owner_id=%s
GROUP BY yourappname_category.id, yourappname_category.name"""

categories = Category.objects.raw(q, [obj.id, user.id])
results = [{'id': c.id, 'name': c.name, 'added': c.added} for c in categories]

Answer 2

如果我正确理解您的用例，您只需要检查用户的帖子（Outfit）添加到＆＃34;的类别。为此你只需要返回添加= true的那些吗？然后你可以保留添加的密钥。

如：

"categories": [{
        "id": 1,
        "name": "Gym"
    }, {
        "id": 3,
        "name": "hollymo"
    }
]

如果是这样，你可以使用：

import Category from category.models

class CategoriesSerializer(serializers.ModelSerializer):

    class Meta:
        model = Category
        fields = ('id', 'name')

class OutfitDetailSerializer(serializers.ModelSerializer):
    categories = CategoriesSerializer(many=True)

如果您的用例是显示所有类别的列表，然后只添加当前装备添加到的类别，我建议执行2次API调用而不是当前逻辑;一个有我上面提供的答案，一个得到所有类别。然后这样做＆＃39;添加＆＃39;前端的逻辑作为其表示层逻辑imo。

我当然会尽量避免在Django中进行原始SQL查询，这会削弱迁移的目的，而且很少需要。

你能优化这段代码吗？（Django，python）

2 个答案:

你能优化这段代码吗？ （Django，python）

2 个答案:

你能优化这段代码吗？（Django，python）