Django 模型空白=假不起作用? [英] Django model blank=False does not work?

问题描述

我在 Django 1.5 中有以下模型:

I have the following model in Django 1.5:

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

注意根据https://docs.djangoproject.com/en/dev/ref/模型/字段/name.blank 默认为 False，这意味着它必须被指定.

Note that according to https://docs.djangoproject.com/en/dev/ref/models/fields/ name.blank is by default False which means it must be specified.

但是，我可以成功创建一个 Person 对象，如下所示:

However, I could successfully create a Person object as follows:

Person.objects.create()

请注意未指定名称.这是怎么回事?

Notice the name is not specified. What is going on?

好的，文档的答案是:

请注意，这与 null 不同.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=True，表单验证将允许输入一个空值.如果某个字段有空白 = False，则该字段将是必需的.

Note that this is different than null. null is purely database-related, whereas blank is validation-related. If a field has blank=True, form validation will allow entry of an empty value. If a field has blank=False, the field will be required.

另一个问题:

请注意，当您保存模型时，验证器不会自动运行，但如果您使用的是 ModelForm，它将在表单中包含的任何字段上运行您的验证器.

Note that validators will not be run automatically when you save a model, but if you are using a ModelForm, it will run your validators on any fields that are included in your form.

如果您不使用表单，则有责任在保存之前调用 clean 方法.

It's your responsibility to call the clean methods before saving if you're not using a form.

推荐答案

blank 仅适用于表单字段验证，如 admin、django 表单等.
null 另一方面是数据库级别的可空列.

blank only applies to form field validation as in the admin, django forms, etc.
null on the other hand is a database level nullable column.

至于为什么空白会导致默认的 ''，我真的只是接受它，因为这就是它的工作方式"，但它似乎出现在 django.db 中.模型.字段

As for why blank results in a default '', I had really just accepted it as "that's the way it works" but here's where it appears to be in django.db.models.Field

  def get_default(self):
        """
        Returns the default value for this field.
        """
        if self.has_default():
            if callable(self.default):
                return self.default()
            return force_unicode(self.default, strings_only=True)
        if (not self.empty_strings_allowed or (self.null and
                   not connection.features.interprets_empty_strings_as_nulls)):
            return None
        return ""  
        #       ^ this

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