扩展表单字段以添加新的验证

Question

我编写了一个应用程序，它使用表单收集信息，然后通过电子邮件发送。其中许多表单都有一个用于将文件附加到电子邮件的文件字段。我想验证两件事，文件的大小（以确保我们的邮件服务器接受电子邮件。我还想检查文件扩展名，以阻止附加对我们的用户不可用的文件类型。

（这是我要扩展的python类）

class FileField(Field):
    widget = FileInput
    default_error_messages = {
        'invalid': _(u"No file was submitted. Check the encoding type on the form."),
        'missing': _(u"No file was submitted."),
        'empty': _(u"The submitted file is empty."),
        'max_length': _(u'Ensure this filename has at most %(max)d characters (it has %(length)d).'),
    }

    def __init__(self, *args, **kwargs):
        self.max_length = kwargs.pop('max_length', None)
        super(FileField, self).__init__(*args, **kwargs)

    def clean(self, data, initial=None):
        super(FileField, self).clean(initial or data)
        if not self.required and data in EMPTY_VALUES:
            return None
        elif not data and initial:
            return initial

        # UploadedFile objects should have name and size attributes.
        try:
            file_name = data.name
            file_size = data.size
        except AttributeError:
            raise ValidationError(self.error_messages['invalid'])

        if self.max_length is not None and len(file_name) > self.max_length:
            error_values =  {'max': self.max_length, 'length': len(file_name)}
            raise ValidationError(self.error_messages['max_length'] % error_values)
        if not file_name:
            raise ValidationError(self.error_messages['invalid'])
        if not file_size:
            raise ValidationError(self.error_messages['empty'])
    return data

Answer 1

只需重载“clean”方法：

def clean(self, data, initial=None):
    try:
        if data.size > somesize:
            raise ValidationError('File is too big')

        (junk, ext) = os.path.splitext(data.name)
        if not ext in ('.jpg', '.gif', '.png'):
            raise ValidationError('Invalid file type')

    except AttributeError:
        raise ValidationError(self.error_messages['invalid'])

    return FileField.clean(self, data, initial)

Answer 2

在我看来，子类化实际的字段类需要付出很多努力。简单地扩展您的表单类应该更容易。您可以添加一个“清理”文件字段的方法。

例如：

class MyForm(forms.Form):
  attachment = forms.FileField(...)

  def clean_attachment(self):
    data = self.cleaned_data['attachment'] // UploadedFile object
    exts = ['jpg', 'png'] // allowed extensions

    // 1. check file size
    if data.size > x:
      raise forms.ValidationError("file to big")

    // 2. check file extension
    file_extension = data.name.split('.')[1] // simple method

    if file_extension not in exts:
      raise forms.ValidationError("Wrong file type")

    return data

这只是一个基本的例子，还有一些粗糙的地方。但是您可以使用此示例并对其进行改进，直到找到适合您的版本。

推荐阅读：

Django Doc - Cleaning a specific field

Django Doc - UploadedFile class

Django Doc - File class

Answer 3

这就是我最终做的：

在我应用的设置文件中：

exts = ['doc', 'docx', 'pdf', 'jpg', 'png', 'xls', 'xlsx', '.xlsm', '.xlsb']
max_email_attach_size = 10485760 #10MB written in bytes

在一个名为 formfunctions 的新文件中：

from django import forms
from django.forms.util import ErrorList, ValidationError
from app.settings import exts, max_email_attach_size


class SizedFileField(forms.FileField):

    def clean(self, data, initial=None):

        if not data in (None, ''):

            try:
                if data.size > max_email_attach_size:
                    raise ValidationError("The file is too big")

                file_extension = data.name.split('.')[1]
                if file_extension not in exts:
                    raise ValidationError("Invalid File Type")

            except AttributeError:
                raise ValidationError(self.error_messages['invalid'])

        return forms.FileField.clean(self, data, initial)

在我的表单文件中：

from formfunctions import SizedFileField

表单文件中的示例类：

class ExampleClass(forms.Form):
    Email_Body = forms.CharField(widget=forms.Textarea, required=False)
    Todays_Date = forms.CharField()
    Attachment = SizedFileField(required=False)