models.py

Question

我有3个依赖下拉列表的乡村城市之路。

从数据库中预先填充国家/地区，然后根据第一个国家/地区的选择显示相关城市。

问题在于，一旦用户从第一个下拉列表中进行选择，系统就会显示以下错误：

all_cities = selected_country.City_set.all（）AttributeError： “国家”对象没有属性“城市集”

我不知道如何解决此错误。

models.py

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

    def __str__(self):
        return str(self.name)

class City(models.Model):
    name = models.CharField(max_length=100)
    country = models.ForeignKey(Country,on_delete=models.CASCADE)



    def __str__(self):
        # return'id : {0} MouhafazatID :{1} Name :{2}'.format(self.id,self.MouhafazatID,self.name)
        return str(self.name)

class Road(models.Model):
    Vil = models.CharField(max_length=100)
    city= models.ForeignKey(City,on_delete = models.SET_NULL, null=True)
    country= models.ForeignKey(Country,on_delete = models.SET_NULL,null=True)

    def __str__(self):
        return str(self.Vil)

home2.html

<html>
    <head>
    <script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"></script>

        <script>
             $(document).ready(function(){
             $('select#selectcountries').change(function () {
                 var optionSelected = $(this).find("option:selected");
                 var valueSelected  = optionSelected.val();
                 var country_name   = optionSelected.text();


                 data = {'cnt' : country_name };
                 alert(country_name);
                 $.ajax({
                     type:"GET",
                     url:'/getdetails',
                     // data:JSON.stringify(data),
                     data:data,
                     success:function(result){
                        console.log(result);
                        $("#selectcities option").remove();
                        for (var i = result.length - 1; i >= 0; i--) {
                            $("#selectcities").append('<option>'+ result[i].name +'</option>');
                        };
                      },
                });
            });
        });
        </script>
    </head>

    <body>
        <select name="selectcountries" id="selectcountries">
        {% for item in countries %}
            <option val="{{ item.name }}"> {{ item.name }} </option>    
        {% endfor %}
        </select>   


        <select name ="selectcities" id="selectcities">


        </select>       

        <select name ="selectroads" id="selectroads">


        </select>



    </body>
</html>

views.py

from django.shortcuts import render,redirect

from django.http import HttpResponse,JsonResponse
from testapp.models import *

import json as simplejson



def home2(request):
    countries = Country.objects.all()
    print("countries =", countries)
    return render(request, 'home2.html',{'countries': countries})



def getdetails(request):
    if request.method == 'GET' and request.is_ajax():
        country_name = request.GET.get('cnt', None) 
        print ("ajax country_name ", country_name)

        result_set = []
        all_cities = []

        answer = str(country_name[1:-1])
        print('answer = ' ,answer)
        selected_country = Country.objects.get(name=answer)
        print ("selected country name ", selected_country)

        all_cities = selected_country.City_set.all()
        print("cities are: " , all_cities)
        for city in all_cities:
            print ("city name", city.name)
            result_set.append({'name': city.name})

        return HttpResponse(simplejson.dumps(result_set),content_type='application/json')
        # return JsonResponse(result_set,status = 200)

    else:
        return redirect('/')

如您所见，我正在以json格式传递数据。

，但 views.py 中的函数会执行到这一行

print ("selected country name ", selected_country)

具有正确的值。

，然后显示错误。

Answer 1

使用小写字母时，您需要将City_set替换为city_set。

Answer 2

访问反向外键关系时，在提及相关模型时始终使用小写字母。是

all_cities = selected_country.city_set.all()

为提高可读性，在声明外键字段时，请使用related_name属性。示例：

class City(models.Model):
    name = models.CharField(max_length=100)
    country = models.ForeignKey(Country, on_delete=models.CASCADE, related_name='cities')

通过添加上面的related_name属性，您可以按以下方式访问城市：

all_cities = selected_country.cities.all()

如何解决错误AttributeError：'Country'对象没有属性'City_set'。在Django

models.py

home2.html

views.py

2 个答案: