带有DRF的Django过滤器-使用相同的查找应用多个值时如何执行“和"操作? [英] Django-filter with DRF - How to do 'and' when applying multiple values with the same lookup?

问题描述

这是我正在使用的过滤器集的稍微简化的示例，我将其与Django Rest Framework的DjangoFilterBackend一起使用.我希望能够向/api/bookmarks/?title__contains=word1&title__contains=word2发送请求并返回包含两个单词的结果，但是当前它忽略第一个参数，并且仅过滤word2.

This is a slightly simplified example of the filterset I'm using, which I'm using with the DjangoFilterBackend for Django Rest Framework. I'd like to be able to send a request to /api/bookmarks/?title__contains=word1&title__contains=word2 and have results returned that contain both words, but currently it ignores the first parameter and only filters for word2.

任何帮助将不胜感激！

class BookmarkFilter(django_filters.FilterSet):

    class Meta:
        model = Bookmark
        fields = {
            'title': ['startswith', 'endswith', 'contains', 'exact', 'istartswith', 'iendswith', 'icontains', 'iexact'],
        }

class BookmarkViewSet(viewsets.ModelViewSet):
    serializer_class = BookmarkSerializer
    permission_classes = (IsAuthenticated,)
    filter_backends = (DjangoFilterBackend,)
    filter_class = BookmarkFilter
    ordering_fields = ('title', 'date', 'modified')
    ordering = '-modified'
    page_size = 10

推荐答案

主要问题是您需要一个了解如何对多个值进行运算的过滤器.基本上有两种选择:

The main problem is that you need a filter that understands how to operate on multiple values. There are basically two options:

• 使用MultipleChoiceFilter(此实例不推荐)
• 编写自定义过滤器类

• Use MultipleChoiceFilter (not recommended for this instance)
• Write a custom filter class

使用MultipleChoiceFilter

Using MultipleChoiceFilter

class BookmarkFilter(django_filters.FilterSet):
    title__contains = django_filters.MultipleChoiceFilter(
        name='title',
        lookup_expr='contains',
        conjoined=True,  # uses AND instead of OR
        choices=[???],
    )

    class Meta:
        ...

虽然这保留了您所需的语法，但问题是您必须构造一个选择列表.我不确定是否可以简化/减少可能的选择，但是袖手旁观似乎需要从数据库中获取所有标题，将标题拆分为不同的词，然后创建一个集合以删除重复项.根据您拥有的记录数量，这似乎是昂贵/缓慢的.

While this retains your desired syntax, the problem is that you have to construct a list of choices. I'm not sure if you can simplify/reduce the possible choices, but off the cuff it seems like you would need to fetch all titles from the database, split the titles into distinct words, then create a set to remove duplicates. This seems like it would be expensive/slow depending on how many records you have.

自定义Filter

Custom Filter

或者，您可以创建一个自定义过滤器类-类似于以下内容:

Alternatively, you can create a custom filter class - something like the following:

class MultiValueCharFilter(filters.BaseCSVFilter, filters.CharFilter):
    def filter(self, qs, value):
        # value is either a list or an 'empty' value
        values = value or []

        for value in values:
            qs = super(MultiValueCharFilter, self).filter(qs, value)

        return qs


class BookmarkFilter(django_filters.FilterSet):
    title__contains = MultiValueCharFilter(name='title', lookup_expr='contains')

    class Meta:
        ...

用法(请注意，这些值以逗号分隔):

Usage (notice that the values are comma-separated):

GET /api/bookmarks/?title__contains=word1,word2

结果:

qs.filter(title__contains='word1').filter(title__contains='word2')

语法稍有变化，但是基于CSV的过滤器不需要构造不必要的选择集.

The syntax is changed a bit, but the CSV-based filter doesn't need to construct an unnecessary set of choices.

请注意，由于小部件无法呈现合适的html输入，因此实际上不可能支持?title__contains=word1&title__contains=word2语法.您可能需要使用SelectMultiple(再次需要选择)，或在客户端上使用javascript添加/删除具有相同name属性的其他文本输入.

Note that it isn't really possible to support the ?title__contains=word1&title__contains=word2 syntax as the widget can't render a suitable html input. You would either need to use SelectMultiple (which again, requires choices), or use javascript on the client to add/remove additional text inputs with the same name attribute.

无需赘述，过滤器和过滤器集只是Django形式的扩展.

Without going into too much detail, filters and filtersets are just an extension of Django's forms.

• Filter具有形式Field，而形式又具有Widget.
• FilterSet由Filter个组成.
• FilterSet根据其过滤器的字段生成内部形式.

• A Filter has a form Field, which in turn has a Widget.
• A FilterSet is composed of Filters.
• A FilterSet generates an inner form based on its filters' fields.

每个过滤器组件的职责:

Responsibilities of each filter component:

• 窗口小部件从data

• The widget retrieves the raw value from the data QueryDict.
• The field validates the raw value.
• The filter constructs the filter() call to the queryset, using the validated value.

为了对同一过滤器应用多个值，您将需要一个过滤器，字段和小部件，它们了解如何对多个值进行操作.

In order to apply multiple values for the same filter, you would need a filter, field, and widget that understand how to operate on multiple values.

自定义过滤器通过混入BaseCSVFilter来实现此目的，该函数又将逗号分隔=>列表"功能混入组成的字段和窗口小部件类中.

The custom filter achieves this by mixing in BaseCSVFilter, which in turn mixes in a "comma-separation => list" functionality into the composed field and widget classes.

我建议您查看CSV mixins的源代码，但总之:

I'd recommend looking at the source code for the CSV mixins, but in short:

• 小工具将传入的值拆分为值列表.
• 字段通过验证主"字段类(例如CharField或IntegerField)上的各个值来验证整个值列表.该字段还可以导出混合窗口小部件.
• 过滤器只需派生混合字段类.

• The widget splits the incoming value into a list of values.
• The field validates the entire list of values by validating individual values on the 'main' field class (such as CharField or IntegerField). The field also derives the mixed in widget.
• The filter simply derives the mixed in field class.

该CSV过滤器旨在与in和range查找一起使用，这些查找接受值列表.在这种情况下，contains需要单个值. filter()方法通过遍历值并将各个过滤器调用链接在一起来解决此问题.

The CSV filter was intended to be used with in and range lookups, which accept a list of values. In this case, contains expects a single value. The filter() method fixes this by iterating over the values and chaining together individual filter calls.

这篇关于带有DRF的Django过滤器-使用相同的查找应用多个值时如何执行“和"操作?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！