如何在 WTForms 中使字段有条件地可选？

Question

我的表单验证工作已接近完成，我只有 2 种情况，我不知道如何解决：1）密码字段当然应该是必需的，但我也提供了使用 google 或 facebook 帐户登录的可能性通过 OAuth，然后预先填写名称，但我从表单中完全删除密码字段是否存在用户（谷歌）或 facebook 用户对象：

<tr><td>
  <br />        {% if user or current_user %}    {% else %} 

  <div class="labelform">
     {% filter capitalize %}{% trans %}password{% endtrans %}{% endfilter %}:
  </div>
      </td><td>  <div class="adinput">{{ form.password|safe }}{% trans %}Choose a password{% endtrans %}</div>{% endif %}

  </td></tr>

所以对于这些已经登录并且密码字段没有意义的用户，我需要一些逻辑来使该字段有条件地可选。我在想我可以在我的表单类中有一个用于logged_in的变量+一个方法，例如：

class AdForm(Form):
    logged_in = False
    my_choices = [('1', _('VEHICLES')), ('2', _('Cars')), ('3', _('Bicycles'))]
    name = TextField(_('Name'), [validators.Required(message=_('Name is required'))], widget=MyTextInput())
    title = TextField(_('title'), [validators.Required(message=_('Subject is required'))], widget=MyTextInput())
    text = TextAreaField(_('Text'),[validators.Required(message=_('Text is required'))], widget=MyTextArea())
    phonenumber = TextField(_('Phone number'))
    phoneview = BooleanField(_('Display phone number on site'))
    price = TextField(_('Price'),[validators.Regexp('\d', message=_('This is not an integer number, please see the example and try again')),validators.Optional()] )
    password = PasswordField(_('Password'),[validators.Optional()], widget=PasswordInput())
    email = TextField(_('Email'), [validators.Required(message=_('Email is required')), validators.Email(message=_('Your email is invalid'))], widget=MyTextInput())
    category = SelectField(choices = my_choices, default = '1')

    def validate_name(form, field):
        if len(field.data) > 50:
            raise ValidationError(_('Name must be less than 50 characters'))

    def validate_email(form, field):
        if len(field.data) > 60:
            raise ValidationError(_('Email must be less than 60 characters'))

    def validate_price(form, field):
        if len(field.data) > 8:
            raise ValidationError(_('Price must be less than 9 integers'))

    def validate_password(form, field):
        if not logged_in and not field:
            raise ValidationError(_('Password is required'))

上面的 validate_password 能否达到预期的效果？还有其他更好的方法吗？我能想到的另一种方法是有 2 个不同的表单类，在 http 帖子中我实例化了它应该是的表单类：

def post(self):
    if not current_user:
      form = AdForm(self.request.params)
    if current_user:
      form = AdUserForm(self.request.params)

I also need conditional validation for the category field, when a certain category is selected then more choices appear and these should have validation only for a certain base-category eg.用户选择“汽车”，然后通过 Ajax 可以选择汽车的注册数据和里程数，鉴于选择了汽车类别，这些字段是必需的。

所以这可能是两个问题，但两种情况都与我如何使字段“有条件可选”或“有条件要求”有关。

我的表单是这样的

对于登录用户，我预先填写了姓名和电子邮件地址，而密码字段根本没有使用，因此密码字段既不适合“可选”也不适合“必需”，它需要类似“有条件可选”或“有条件地要求。”

感谢您的任何回答或评论

Answer 1

我不确定这是否完全符合您的需求，但我之前在字段上使用过 RequiredIf 自定义验证器，如果另一个字段在表单中具有值，则该字段是必需的......例如，在在日期时间和时区场景中，如果用户输入了日期时间，我可以使时区字段必须具有值。

class RequiredIf(Required):
    # a validator which makes a field required if
    # another field is set and has a truthy value

    def __init__(self, other_field_name, *args, **kwargs):
        self.other_field_name = other_field_name
        super(RequiredIf, self).__init__(*args, **kwargs)

    def __call__(self, form, field):
        other_field = form._fields.get(self.other_field_name)
        if other_field is None:
            raise Exception('no field named "%s" in form' % self.other_field_name)
        if bool(other_field.data):
            super(RequiredIf, self).__call__(form, field)

构造函数采用触发使该字段成为必需的另一个字段的名称，例如：

class DateTimeForm(Form):
    datetime = TextField()
    timezone = SelectField(choices=..., validators=[RequiredIf('datetime')])

这可能是实现所需逻辑的良好起点。

Answer 2

我发现这个问题很有帮助，根据@dcrosta 的回答，我创建了另一个可选的验证器。好处是您可以将它与其他 wtforms 验证器结合使用。这是我的可选验证器，它检查另一个字段。因为我需要根据某个特定值检查另一个字段的值，所以我添加了一个自定义值检查：

class OptionalIfFieldEqualTo(wtf.validators.Optional):
    # a validator which makes a field optional if
    # another field has a desired value

    def __init__(self, other_field_name, value, *args, **kwargs):
        self.other_field_name = other_field_name
        self.value = value
        super(OptionalIfFieldEqualTo, self).__init__(*args, **kwargs)

    def __call__(self, form, field):
        other_field = form._fields.get(self.other_field_name)
        if other_field is None:
            raise Exception('no field named "%s" in form' % self.other_field_name)
        if other_field.data == self.value:
            super(OptionalIfFieldEqualTo, self).__call__(form, field)

Answer 3

@dcrosta 的答案很棒，但我认为自从这个答案以来，wtforms 中的一些事情已经发生了变化。从DataRequired 继承会向表单字段添加required 属性，因此条件验证器永远不会被调用。我对与 wtforms 2.1 一起使用的 @dcrosta 类进行了细微更改。这只会覆盖field_flags，因此不会完成浏览器验证。

from wtforms.validators import DataRequired


class RequiredIf(DataRequired):
    """Validator which makes a field required if another field is set and has a truthy value.

    Sources:
        - http://wtforms.simplecodes.com/docs/1.0.1/validators.html
        - http://stackoverflow.com/questions/8463209/how-to-make-a-field-conditionally-optional-in-wtforms

    """
    field_flags = ('requiredif',)

    def __init__(self, other_field_name, message=None, *args, **kwargs):
        self.other_field_name = other_field_name
        self.message = message

    def __call__(self, form, field):
        other_field = form[self.other_field_name]
        if other_field is None:
            raise Exception('no field named "%s" in form' % self.other_field_name)
        if bool(other_field.data):
            super(RequiredIf, self).__call__(form, field)

更理想的解决方案是设法在浏览器中进行验证，例如 DataRequired 的当前行为。