Django CBV 更新 ValueError 无法分配无

Question

创建初始数据 (CreateView) 后，我继续更新更多数据 (UpdateView)，但在尝试更新新数据时得到以下答案。我附上代码的相关部分：

ValueError at /preinscripcion/padres/63
Cannot assign None: "Alumni.cycle" does not allow null values.
Request Method: POST
Request URL:    http://decroly.administracionescolarmexico.com/preinscripcion/padres/63
Django Version: 1.5
Exception Type: ValueError
Exception Value:    
Cannot assign None: "Alumni.cycle" does not allow null values.
Exception Location: /home/fbenavides/webapps/django/lib/python2.7/django/db/models/fields/related.py in __set__, line 401
Python Executable:  /usr/local/bin/python
Python Version: 2.7.5

模型.py

# -*- coding: utf-8 -*-
# Create your models here
from django.db    import models
from django.forms import ModelForm
from django.conf  import settings
from django.core.files.storage import FileSystemStorage
import os.path
import datetime

# Create your models here
class ScholarCycle(models.Model):
"""
ScholarCycle
Yearly School Cycle (e.g. 2012-2013)
"""
cycle = models.CharField(blank=False, max_length=9, verbose_name=u'Ciclo Escolar')

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

class Meta:
    db_table = u'Ciclo Escolar'
    ordering = ['id', 'cycle']
    verbose_name = u'Ciclo Escolar'
    verbose_name_plural = u'Ciclos Escolares'

class Admin:
    pass

fs_photos = FileSystemStorage(location='/media/user/photos')
fs_docs   = FileSystemStorage(location='/media/user/docs')

class Alumni(models.Model):
"""
"""
cycle = models.ForeignKey(ScholarCycle, unique=False, null=False, blank=True, verbose_name=u'Ciclo Escolar')

url.py

urlpatterns = patterns('',
url(r'^lista/$', views.AlumniList.as_view(), name='alumni-lista'),
url(r'^lista/(?P<page>\d+)$', views.AlumniRedirectMostrar.as_view(), name='alumni-redirect-mostrar'),
url(r'^mostrar/(?P<pk>\d+)$', views.AlumniRetrieve.as_view(), name='alumni-mostrar'),
url(r'^mostrar/padres/(?P<pk>\d+)$', views.AlumniRetrievePadres.as_view(), name='alumni-mostrar-padres'),
url(r'^mostrar/autorizado/(?P<pk>\d+)$', views.AlumniRetrieveAutorizado.as_view(), name='alumni-mostrar-autorizado'),
url(r'^mostrar/finanzas/(?P<pk>\d+)$', views.AlumniRetrieveFinanzas.as_view(), name='alumni-mostrar-finanzas'),
url(r'^mostrar/documentos/(?P<pk>\d+)$', views.AlumniRetrieveDocumentos.as_view(), name='alumni-mostrar-documentos'),
url(r'^inscripcion/$', views.AlumniRegister.as_view(), name='alumni-inscripcion'),
url(r'^inscripcion/padres/(?P<pk>\d+)$', views.AlumniRegisterPadres.as_view(), name='alumni-inscripcion-padres'),
url(r'^inscripcion/autorizado/(?P<pk>\d+)$', views.AlumniRegisterAutorizado.as_view(),      name='alumni-inscripcion-autorizado'),
url(r'^inscripcion/finanzas/(?P<pk>\d+)$', views.AlumniRegisterFinanzas.as_view(),        name='alumni-inscripcion-finanzas'),
url(r'^inscripcion/documentos/(?P<pk>\d+)$', views.AlumniRegisterDocumentos.as_view(),      name='alumni-inscripcion-documentos'),
url(r'^preinscripcion/$', views.AlumniPreinscripcion.as_view(), name='alumni-preinscripcion'),
url(r'^preinscripcion/padres/(?P<pk>\d+)$', views.AlumniPreinscripcionPadres.as_view(),      name='alumni-preinscripcion-padres'),
url(r'^preinscripcion/autorizados/(?P<pk>\d+)$', views.AlumniPreinscripcionAutorizados.as_view(), name='alumni-preinscripcion-autorizados'),
url(r'^preinscripcion/finanzas/(?P<pk>\d+)$',    views.AlumniPreinscripcionFinanzas.as_view(),    name='alumni-preinscripcion-finanzas'),

views.py

class AlumniPreinscripcion(LoginRequiredMixin, CreateView):
    model               = models.Alumni
    form_class          = forms.AlumniFormPreinscripcion
    context_object_name = 'alumno'
    template_name       = 'alumni_preinscripcion.html'
    def get_initial(self):
        initial = super(AlumniPreinscripcion, self).get_initial()
        initial['cycle'] = models.ScholarCycle.objects.get(cycle__exact='2014-2015')
        return initial
    def get_success_url(self, **kwargs):
        return reverse('alumni-preinscripcion-padres', kwargs={'pk':self.object.id})

class AlumniPreinscripcionPadres(LoginRequiredMixin, UpdateView):
    model               = models.Alumni
    form_clas           = forms.AlumniFormPreinscripcionPadres
    context_object_name = 'alumno'
    template_name       = 'alumni_preinscripcion_padres.html'
    def get_sucess_url(self, **kwargs):
        return reverse('alumni-preinscripcion-autorizados', kwargs='pk':self.object.id})

alumni_preinscripcion_padres.html

{% extends "preinscripcion.html" %}
{% load i18n %}
{% load l10n %}

{% block content %}
  <h2>Padres</h2>
  <form action="" method="post" enctype="multipart/form-data" accept-charset="utf-8">
    {% csrf_token %}

    <fieldset>
      <legend><strong>&nbsp;Pap&aacute;&nbsp;</strong></legend>
      <div class="row-fluid">
        <div class="span2">
          <p>Nombre:</p>
        </div>
        <div class="span10">
          <p>{{ form.father_name }} {{ form.father_familynames }}</p>
        </div>
      </div>

    <br />
    <p><input type="submit" value="Persona(s) Autorizada(s) &rarr;" /></p>
  </form>
{% endblock %}

Answer 1

Alumni 模型上的 cycle 字段是用 null=False, blank=True 定义的。你可能想改变它。我无法告诉您 正确 值，因为这取决于您的应用程序逻辑，但这些值与您的表单视图不一致。来自documention：

null 纯粹与数据库相关，而空白与验证相关。 如果一个字段有空白=真，表单验证将允许输入 空值。如果某个字段的空白=False，则该字段为必填项。

阅读整个部分。一旦您了解了模型字段的正确设置，表单和基于类的视图很可能会正常工作。 （仅供参考，您的 CreateView 工作的原因是因为您专门设置了满足空标准的 initial['cycle']，而您在 UpdateView 中没有这样做，并且更新表单认为可以使用空白/空值。）

更新：您的 AlumniPreinscripcionPadres 视图中有两个拼写错误，get_sucess_url() 和 form_clas，都缺少一个字母。