保存带下拉菜单的表单集时出现完整性错误：XXX_id 不能为空

Question

我正在尝试创建一个表单集合，其中每个表单（PropertySelector）都有一个下拉菜单（PropertySelector.property），而这个菜单中的每个选项都是指向另一个模型（Property）的外键引用。

但是，当我尝试提交并保存这个表单集合时，我遇到了以下问题：

Exception Type:     IntegrityError
Exception Value:    testproj_propertyselector.property_id may not be NULL

这是什么问题，我该如何解决呢？我的完整代码在下面。谢谢。

编辑：我觉得这可能是inline_formset的问题（也可能和MySQL有关）。请帮我想个解决办法。

这个项目叫做testproj，我的应用程序也叫testproj。

首先，我们需要填充Property：

>>> from testproj.models import Property
>>> p = Property(name='prop1', basic=True)
>>> p.save() 
>>> p = Property(name='prop2', basic=True)
>>> p.save()

models.py

from django.db import models

class PropertySet(models.Model):
    name = models.CharField(max_length=50)

class Property(models.Model):
    name = models.CharField(max_length=50)
    basic = models.BooleanField()

    def __unicode__(self):
        return u'%s' % (self.name)

class PropertySelector(models.Model):
    property_set = models.ForeignKey(PropertySet)
    title = models.CharField(max_length=50)
    property = models.ForeignKey(Property)

forms.py

from django.forms import ModelForm, TextInput, Select, ModelChoiceField
from django.db.models import Q
from testproj.models import Property, PropertySet, PropertySelector

class PropertySetForm(ModelForm):
    class Meta:
        model = PropertySet

def PropertySelForm():
    PropertyQueryset = Property.objects.filter(Q(basic=True))

    class PropertySelectorForm(ModelForm):
        property = ModelChoiceField(
            queryset=PropertyQueryset,
            widget=Select(attrs={'class': 'property'})
        )

        def __init__(self, *args, **kwargs): 
            super(ModelForm, self).__init__(*args, **kwargs)
            self.css_class = "prop_sel"

        class Meta:
            model = PropertySelector
            fields = ("property_set", "title")
            widgets = {"title" : TextInput(attrs={"class" : "title"})}

    return PropertySelectorForm

views.py

from django.shortcuts import render_to_response
from django.template import RequestContext
from django.forms.models import inlineformset_factory

from testproj.models import PropertySet, PropertySelector
from testproj.forms import PropertySetForm, PropertySelForm, PropertySelForm

def index(request):

    property_selector_form = PropertySelForm()
    PropertySelectorFormSet = inlineformset_factory(PropertySet, PropertySelector, form=property_selector_form)

    if request.method == "POST":

        property_set_form = PropertySetForm(request.POST)

        if property_set_form.is_valid():            
            saved_property_set = property_set_form.save()

            prop_sel_formset = PropertySelectorFormSet(request.POST, instance=saved_property_set)

            if prop_sel_formset.is_valid():
                prop_sel_formset.save()

        else:

            property_set_form = PropertySetForm()

            prop_sel_formset = PropertySelectorFormSet()    

        return render_to_response(
            "testproj/index.html",
            {
                "property_set_form": property_set_form,
                "prop_sel_formset": prop_sel_formset
            },
            context_instance=RequestContext(request)
        )

index.html（模板）：

{% block content %}

<head>

</head>

<body>

<form method="post" action=""> {% csrf_token %}

    {{ property_set_form.as_p }}

    {{ prop_sel_formset.management_form }}

    {% for form in prop_sel_formset %}
        {{ form }}

    {% endfor %}

    <input type="submit" value="Submit">    
</form>

</body>
{% endblock %}

mysql django 表单验证模型设计下拉菜单外键引用完整性错误 inline_formset

保存带下拉菜单的表单集时出现完整性错误：XXX_id 不能为空

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