Django 在保存对象之前处理文件上载

我有一个这样的模型：

class Talk(BaseModel):
  title        = models.CharField(max_length=200)
  mp3          = models.FileField(upload_to = u'talks/', max_length=200)
  seconds      = models.IntegerField(blank = True, null = True)

def is_mp3(path_to_file):
  from mutagen.mp3 import MP3
  audio = MP3(path_to_file)
  return not audio.info.sketchy

audio = MP3(path_to_file)
self.seconds = audio.info.length

from django.core.exceptions import ValidationError

#this go in your class Model
def clean(self):
    try:
        f = self.mp3.file #the file in Memory
    except ValueError:
        raise ValidationError("A File is needed")
    f.__class__ #this prints <class 'django.core.files.uploadedfile.InMemoryUploadedFile'>
    processfile(f)

我想在保存之前验证上传的文件是否是MP3，如下所示：

class Talk(BaseModel):
  title        = models.CharField(max_length=200)
  mp3          = models.FileField(upload_to = u'talks/', max_length=200)
  seconds      = models.IntegerField(blank = True, null = True)

def is_mp3(path_to_file):
  from mutagen.mp3 import MP3
  audio = MP3(path_to_file)
  return not audio.info.sketchy

audio = MP3(path_to_file)
self.seconds = audio.info.length

from django.core.exceptions import ValidationError

#this go in your class Model
def clean(self):
    try:
        f = self.mp3.file #the file in Memory
    except ValueError:
        raise ValidationError("A File is needed")
    f.__class__ #this prints <class 'django.core.files.uploadedfile.InMemoryUploadedFile'>
    processfile(f)

一旦我确定我有MP3，我想在秒属性中保存通话长度，如下所示：

class Talk(BaseModel):
  title        = models.CharField(max_length=200)
  mp3          = models.FileField(upload_to = u'talks/', max_length=200)
  seconds      = models.IntegerField(blank = True, null = True)

def is_mp3(path_to_file):
  from mutagen.mp3 import MP3
  audio = MP3(path_to_file)
  return not audio.info.sketchy

audio = MP3(path_to_file)
self.seconds = audio.info.length

from django.core.exceptions import ValidationError

#this go in your class Model
def clean(self):
    try:
        f = self.mp3.file #the file in Memory
    except ValueError:
        raise ValidationError("A File is needed")
    f.__class__ #this prints <class 'django.core.files.uploadedfile.InMemoryUploadedFile'>
    processfile(f)

问题是，在保存之前，上传的文件没有路径（请参阅，关闭为

wontfix

），因此我无法处理MP3

我想提出一个很好的验证错误，这样

ModelForm

s就可以显示一个有用的错误（“你这个白痴，你没有上传MP3”之类的）

知道我如何在文件保存之前访问它吗

---

p、 如果有人知道验证文件的更好方法是MP3，我洗耳恭听-我还希望能够处理ID3数据（设置艺术家、专辑、标题，可能还有专辑艺术，所以我需要它可以处理）。

您可以在视图中访问文件数据

---

我认为最好的方法是，覆盖表单，从已清理的数据中获取数据，以您喜欢的方式对其进行验证，然后覆盖并使用有关文件的信息填充您的模型实例，然后保存它。

在保存文件之前获取该文件的更干净方法如下：

class Talk(BaseModel):
  title        = models.CharField(max_length=200)
  mp3          = models.FileField(upload_to = u'talks/', max_length=200)
  seconds      = models.IntegerField(blank = True, null = True)

def is_mp3(path_to_file):
  from mutagen.mp3 import MP3
  audio = MP3(path_to_file)
  return not audio.info.sketchy

audio = MP3(path_to_file)
self.seconds = audio.info.length

from django.core.exceptions import ValidationError

#this go in your class Model
def clean(self):
    try:
        f = self.mp3.file #the file in Memory
    except ValueError:
        raise ValidationError("A File is needed")
    f.__class__ #this prints <class 'django.core.files.uploadedfile.InMemoryUploadedFile'>
    processfile(f)

来自django.core.exceptions的

导入验证错误
#这是你的课堂模式
def清洁（自清洁）：
尝试：
f=self.mp3.file#内存中的文件
除值错误外：
引发ValidationError（“需要一个文件”）
f、 _uuuu类uuuu#这张照片
进程文件（f）

---

如果我们需要一个路径，答案是

，您可以使用验证文件头然后返回文件开头的技术

class ImageField(FileField):
    # ...    
    def to_python(self, data):
        f = super(ImageField, self).to_python(data)
        # ...
        # We need to get a file object for Pillow. We might have a path or we might
        # have to read the data into memory.
        if hasattr(data, 'temporary_file_path'):
            file = data.temporary_file_path()
        else:
            if hasattr(data, 'read'):
                file = BytesIO(data.read())
            else:
                file = BytesIO(data['content'])

        try:
            # ...
        except Exception:
            # Pillow doesn't recognize it as an image.
            six.reraise(ValidationError, ValidationError(
                self.error_messages['invalid_image'],
                code='invalid_image',
            ), sys.exc_info()[2])
        if hasattr(f, 'seek') and callable(f.seek):
            f.seek(0)
        return f

---

+1并接受！这似乎是要走的路-似乎有点遗憾，没有一种优雅的方式来使用新的模型验证。也许你可以，但它是相当新的，我还不够熟悉它。