具有选择字段的Django表单不提供None作为选择

I have a choice field in a form defined as

我在一个定义为的表单中有一个选择字段

REFERRAL_CHOICES = (
    (None, 'Please choose'),
    ('search', 'From a search engine'),
    ('social', 'From a social network'),
)
referral_source = forms.ChoiceField(
    choices=REFERRAL_CHOICES
)

I also have a clean_company_size function which checks if the field is set to a good value:

我还有一个clean_company_size函数,它检查字段是否设置为一个好的值:

def clean_company_size(self):
    company_size = self.cleaned_data.get('company_size', None)
    if company_size is None:
        raise ValidationError('Please select a company size')

    return company_size

If I add a or company_size == 'None' condition to the above None check, all works well. However, I am curious why the None value is being cast to a string. What is the best way of accomplishing a default prompts in a choice field and having that field be required?

如果我在上面的None检查中添加了a或company_size =='None'条件,则一切正常。但是,我很好奇为什么将None值转换为字符串。在选择字段中完成默认提示并且需要该字段的最佳方法是什么?

1 个解决方案

#1

All POST and GET variables, as well as Select HTML tag values are initially sent as strings. Django converts them to -say- int when it is deductable from the model. In your case it is not possible to distinguish a "None" string from a "None" object, they are both possible values. You may prefer using "" instead of None in your REFERRAL_CHOICHES

所有POST和GET变量以及Select HTML标记值最初都以字符串形式发送。当Django可以从模型中删除时,它们将它们转换为-say-int。在您的情况下,无法区分“无”字符串和“无”对象,它们都是可能的值。您可能更喜欢在REFERRAL_CHOICHES中使用“”而不是“None”