python-如何检查数据库中是否存在对象,然后将其插入到Django的表单中

我有以下模型：models.py

name = models.CharField(max_length=100, blank=False, null=False)
serial_number = models.CharField(max_length=100, blank=False, null=False)
make = models.CharField(max_length=100, blank=False, null=False)
model = models.CharField(max_length=100, blank=False, null=False)
color= models.CharField(max_length=100, blank=False, null=False)
date_acquired = models.DateTimeField(auto_created=True)
acquired_from = models.CharField(max_length=100, choices=ACQUIRED_FROM)
holder = models.ForeignKey(CertificateHolder, blank=False,)
dealer_license = models.ForeignKey(Dealer, blank=False)

我已经使用ModelForm创建了一个表单,如下所示：

class IssueItemForm(ModelForm):

class Meta:
    model = IssuedItem
    fields = '__all__'

经销商需要在签发物品之前检查是否存在证书持有人,我的代码如下所示；

views.py:

def search(request):
try:
    query = request.GET.get('q')
    results = 0

except ValueError:
    query = None
    results = None
if query:
    results = CertificateHolder.objects.get(cert_no=query)

context = RequestContext(request)

return render_to_response('core/results.html', {"results": results, }, context_instance=context)

然后我有模板search.html和results.html

<form method="get" action="/search/">
<input type="text" name="q" id="id_q" value="{{ query }}"/>
<input type="submit" value="Search" />
</form>

在results.html我有

{% if results %}
<h3>The Certificate number is valid</h3>
<h3>To issues an item click the button below</h3>
<a href="{% url 'issueitem' %}">Issue A New Item</a>

{% else %}
<h3 class='error'>Please enter a valid Certificate</h3>
<form method="get" action="/search/">
  <input type="text" name="q" id="id_q" value="{{ query }}"/>
  <input type="submit" value="Search" />
</form>

{% endif %}

如果数据库中有证书,则该代码有效,但是如果不匹配,则会引发如下错误：

error image

但是,我希望该错误成为代码的一部分,以告诉经销商该号码不存在,他应该尝试另一个.另外,当证书存在时,我希望将其插入到holder字段中,而不是像现在那样从数据库中获取证书.我要去哪里错了？

解决方法:

您还必须捕获DidNotExist错误.将if查询改为try try块：

try:
    result = CertificateHolder.objects.get(cert_no=query)
except DoesNotExist:
    pass

标签：django-forms,python,django,django-models
来源： https://codeday.me/bug/20191119/2032247.html