不要将模型保存在重复文件上 - Django 2

我正在尝试检查现有文件并覆盖它，到目前为止我可以使用自定义存储来完成此操作，如下所示

from django.core.files.storage import FileSystemStorage

class DuplicateFileStorage(FileSystemStorage):

    def get_available_name(self, name, max_length=None):

        return name

    def _save(self, name, content):
        if self.exists(name):
            self.delete(name)

        return super(DuplicateFileStorage, self)._save(name, content)

上面的类检查现有文件并将其删除。

它所关注的模型是：

class DataStorageModel(models.Model):

    user = models.ForeignKey(User, related_name='data_storage', on_delete=models.CASCADE)
    file_name = models.CharField(blank=True, max_length=200, help_text="File Name")
    file = models.FileField(blank=True, null=True, upload_to=user_directory_path, storage=DuplicateFileStorage())
    relative_path = models.CharField(blank=True, max_length=200, help_text="Relative Path if folder else null")

    def delete(self, using=None, keep_parents=False):

        self.file.delete()

        return super(DataStorageModel, self).delete()

问题是，虽然它删除并写入相同的文件，但它也会创建一个具有相同现有路径的新模型条目，也就是说，如果我上传相同的文件两次，我会在操作系统路径中得到一个文件，但会得到两个模型条目。像这样的东西（这里有一张图片）：

所以我尝试使用clean()方法与self.file.storage.exists(self.file.name)（根据this https://stackoverflow.com/questions/50606068/how-to-ensure-file-exists-in-django-project）但我得到的存在是False，即使那里有一个文件。

def save(self, force_insert=False, force_update=False, using=None,
         update_fields=None):

    self.full_clean()

    return super(DataStorageModel, self).save()

def clean(self):

    print(self.file.storage.exists(self.file.name))  # <--- False

所以我的问题是，我应该如何检查是否存在重复文件，覆盖该文件但不创建新记录？

Edit

我忘记输入user_director_path():

def user_directory_path(instance, filename):
    """
    If relative path is not ``null`` the files will be stored as is else it will be
    stored to the root directory.
    """

    if instance.relative_path != 'null':
        return 'user_{0}{1}'.format(instance.user.id, instance.relative_path)
    return 'user_{0}/{1}'.format(instance.user.id, filename)

我想如果我这样做我就明白了：

def clean_fields(self, exclude=None):

    if self.file.storage.exists('user_{0}{1}'.format(self.user.id, self.relative_path)):
        raise ValidationError('File already exists.')

它可以工作，但整个上传失败，甚至无法重写文件

条件，if instance.relative_path != 'null':是错的。应该只是if instance.relative_path:

当我尝试你的片段时，我觉得有问题user_directory_path功能。所以，我将其更改为如下所示。

def user_directory_path(instance, filename):
    """
    If relative path is not ``null`` the files will be stored as is else it will be
    stored to the root directory.

    The "relative_path" path should not be start or ends with a slash ("/") but, can use slash inside

    /foo/ -> Not allowed
    /foo/bar -> Not allowed
    foo/bar/ -> Not allowed

    foo -> Allowed
    foo/bar -> Allowed
    foo/bar/foobar -> Allowed

    """

    if instance.relative_path:
        relative_path = instance.relative_path
        if relative_path[0] == '/':
            relative_path = relative_path[1:]
        if relative_path[:-1] == '/':
            relative_path = relative_path[:-1]

        return 'user_{0}/{1}/{2}'.format(instance.user.id, relative_path, filename)
    return 'user_{0}/{1}'.format(instance.user.id, filename)

现在谈到我们的解决方案，我创建了一个示例视图来解决该问题。

from django.http.response import HttpResponse


def foo(request):
    if request.method == 'POST':
        create_data = {
            "user_id": request.user.pk,
            "file": request.FILES['file_name']
        }

        ds_temp = DataStorageModel(**create_data)
        path = user_directory_path(ds_temp, ds_temp.file.name)
        try:
            ds_existing = DataStorageModel.objects.get(file=path)
            ds_existing.file = create_data['file']
            ds_existing.save()
            return HttpResponse("instance modified")
        except DataStorageModel.DoesNotExist:
            ds_temp.save()
            return HttpResponse("new instance created")
    return HttpResponse("HTTP GET method")