Question

我试图通过从多个上下文对象中进行选择来对views.py中的get_context_data进行分页。代码示例条件语句中仅显示了两个选择，但是我还有其他几个选择，它们基本上涵盖了表单提交中的所有选择。仅返回一个上下文，但是最后将上下文传递到模板视图以进行分页。

我也尝试在settings.py中全局设置分页，但是它不起作用。

我以前已经看过下面的文章，作为对get-context-objects进行分页的指南。

How to perform pagination for context object in django?

从views.py：

from django.shortcuts import render
import django.views.generic
from django.http import HttpResponse
from django.template import loader
from django.template import RequestContext
from ephemera.models import *
from ephemera.serializers import ItemSerializer
from rest_framework import generics
from ephemera.forms import SearchForm, AdvSearchForm
from itertools import chain
from django.core.paginator import Paginator
from django.core.paginator import EmptyPage
from django.core.paginator import PageNotAnInteger



class SearchResultsAdvancedView(django.views.generic.ListView): 
    template_name = 'ephemera/searchresults_advanced.html'
    form = AdvSearchForm()
    paginate_by = 10
    model = Item

    def get_context_data(self, **kwargs):       
        context = super(SearchResultsAdvancedView, self).get_context_data(**kwargs)

        choose_collection = self.request.GET.get('choose_collection')
        user_input = self.request.GET.get('user_input')
        choose_item = self.request.GET.get('choose_item')

        bookpage = False
        imagepage = False

        if choose_collection == 'All' and user_input == '' and choose_item == 'book':
            context['book_qs'] = Item.objects.raw('SELECT  * FROM   ephemera_item WHERE ephemera_item.material_type LIKE %s', ['book']);    
            bookpage = True
        elif choose_collection == 'All' and user_input == '' and choose_item == 'image':
            context['image_qs'] = Item.objects.raw('SELECT  * FROM   ephemera_item WHERE ephemera_item.material_type LIKE %s', ['image']);  
            imagepage = True

        if bookpage:
            paginator = Paginator(context, self.paginate_by)            
            page = self.request.GET.get('page')
            try:
                book_qs = paginator.page(page)
            except PageNotAnInteger:
                book_qs = paginator.page(1)
            except EmptyPage:
                book_qs = paginator.page(paginator.num_pages)
            context['book_qs'] = book_qs

        elif imagepage:
            paginator = Paginator(context, self.paginate_by)            
            page = self.request.GET.get('page')
            try:
                image_qs = paginator.page(page)
            except PageNotAnInteger:
                image_qs = paginator.page(1)
            except EmptyPage:
                image_qs = paginator.page(paginator.num_pages)
            context['image_qs'] = image_qs

        return context

返回的错误包括：

异常值：不可散列的类型：'slice'

异常位置：页面70行中的c：\ users \ administrator \ appdata \ local \ programs \ python \ python36-32 \ lib \ site-packages \ django \ core \ paginator.py

Answer 1

这里不需要使用get_context_data [Django-doc]，您可以覆盖get_queryset [Django-doc]和get_context_object_name [Django-doc]来确定模板中列表的名称：

class SearchResultsAdvancedView(django.views.generic.ListView): 
    template_name = 'ephemera/searchresults_advanced.html'
    form = AdvSearchForm()
    paginate_by = 10
    model = Item

    def item_type(self):
        choose_collection = self.request.GET.get('choose_collection')
        if choose_collection != 'All' or not self.request.GET.get('user_input'):
            return None
        choose_item = self.request.GET.get('choose_item')
        if choose_item in ('book', 'image'):
            return choose_item
        return None

    def get_queryset(self, *args, **kwargs):
        item_type = self.get_item_type()
        qs = super.get_queryset(*args, **kwargs)
        if item_type is not None:
            return qs.filter(material_type__iexact=item_type)
        return qs.none()

    def get_context_object_name(self, object_list):
        item_type = self.get_item_type()
        if item_type is not None:
            return '{}_qs'.format(item_type)
        return super().get_context_object_name(object_list)

Django的逻辑将对QuerySet进行分页，因此您不必担心。这是由于get_context_data [Django-doc]的MultipleObjectMixin [Django-doc]实现：

def get_context_data(self, *, object_list=None, **kwargs):
    """Get the context for this view."""
    queryset = object_list if object_list is not None else self.object_list
    page_size = self.get_paginate_by(queryset)
    context_object_name = self.get_context_object_name(queryset)
    if page_size:
        paginator, page, queryset, is_paginated = self.paginate_queryset(queryset, page_size)
        context = {
            'paginator': paginator,
            'page_obj': page,
            'is_paginated': is_paginated,
            'object_list': queryset
        }
    else:
        context = {
            'paginator': None,
            'page_obj': None,
            'is_paginated': False,
            'object_list': queryset
        }
    if context_object_name is not None:
        context[context_object_name] = queryset
    context.update(kwargs)
    return super().get_context_data(**context)

话虽这么说，我的印象是建模做得不好。如果您有项目类型，则可以定义一个ItemType模型。此外，您最好使用Django的ORM来生成查询，而不是原始查询。

Answer 2

原始代码示例中的一个问题是RawQuerySets不适用于get_context_data中显示的分页代码，这些应为带有过滤器的模型对象，否则分页代码将失败。例如。

    mydata = self.model.objects.filter(material_type__icontains = 'book')

但是，在这种情况下，由于具有复杂的内部联接等的附加（未显示）查询等，使用过滤器很难完成，因此需要RawQuerySets并且有用。

One solution for casting a raw query set as a list for pagination is answered in:

还可以使用RawQuerySet的django分页器模块来解决该帖子中链接的此问题。

django-paginator-rawqueryset

借助该模块，原始查询集可以有效地与给定的分页器代码一起使用，以利用上下文对象返回要传递给模板的上下文。然后，该模板以及用于显示页面导航的典型代码，还能够利用附加到上下文的变量来根据需要显示数据。

    {% if book_qs %}
    {% endif %}

    {% if image_qs %}
    {% endif %}

从views.py中显示的问题示例有点“蛮力”，可以借助第一个答案所示的类中的定义进行更紧凑的编码。使用该模块的另一种解决方案，显示在这里：

    from rawpaginator.paginator import Paginator
    from django.core.paginator import EmptyPage
    from django.core.paginator import PageNotAnInteger


    class SearchResultsAdvancedView(django.views.generic.ListView): 
        template_name = 'ephemera/searchresults_advanced.html'
        form = AdvSearchForm()
        paginate_by = 10
        model = Item

        def get_context_data(self, **kwargs):       
            context = super(SearchResultsAdvancedView, self).get_context_data(**kwargs)

            choose_collection = self.request.GET.get('choose_collection')
            user_input = self.request.GET.get('user_input')
            choose_item = self.request.GET.get('choose_item')

            bookpage = False
            imagepage = False

            if choose_collection == 'All' and user_input == '' and choose_item == 'book':
                mydata = Item.objects.raw('SELECT  * FROM   ephemera_item WHERE ephemera_item.material_type LIKE %s', ['book']);    
                bookpage = True
            elif choose_collection == 'All' and user_input == '' and choose_item == 'image':
                mydata = Item.objects.raw('SELECT  * FROM   ephemera_item WHERE ephemera_item.material_type LIKE %s', ['image']);  
                imagepage = True

             paginator = Paginator(mydata, self.paginate_by)            
             page = self.request.GET.get('page')

            if bookpage:
                try:
                    book_qs = paginator.page(page)
                except PageNotAnInteger:
                    book_qs = paginator.page(1)
                except EmptyPage:
                    book_qs = paginator.page(paginator.num_pages)
                context['book_qs'] = book_qs

            elif imagepage:
                try:
                    image_qs = paginator.page(page)
                except PageNotAnInteger:
                    image_qs = paginator.page(1)
                except EmptyPage:
                    image_qs = paginator.page(paginator.num_pages)
                context['image_qs'] = image_qs

            return context

我如何对从多个上下文对象中选择的get_context_data进行分页？

2 个答案: