Question

我正在尝试使用默认的Django管理员创建一个简单的照片库。我想为每个图库保存一张示例照片，但我不想保留该名称。我想保存模型的id（N.jpg），而不是文件名。但是我第一次想要保存对象时id不存在。我怎么知道模型中的下一个自动增量，或者在上传super.save之前以某种方式保存模型数据，并在self.id存在后上传文件？有一个很酷的解决方案吗？

这样的事情：

def upload_path_handler(instance, filename):
    ext = filename extension
    return "site_media/images/gallery/{id}.{ext}".format(id=instance.nextincrement, ext=ext)

class Gallery(models.Model):
    name  = models.TextField()
    image = models.FileField(upload_to=upload_path_handler)

也许可以将文件名存储在不同的字段中。

Answer 1

我遇到了同样的问题。 Okm的回答让我走上了正确的道路，但在我看来，通过覆盖save()方法可以获得相同的功能。

def save(self, *args, **kwargs):
    if self.pk is None:
        saved_image = self.image
        self.image = None
        super(Material, self).save(*args, **kwargs)
        self.image = saved_image

    super(Material, self).save(*args, **kwargs)

这肯定会正确保存信息。

Answer 2

图像文件在Gallery实例之前保存。因此，您必须使用带有状态的图库实例本身的信号将保存分为两个阶段：

from django.db.models.signals import post_save, pre_save
from django.dispatch import receiver

_UNSAVED_FILEFIELD = 'unsaved_filefield'

@receiver(pre_save, sender=Image)
def skip_saving_file(sender, instance, **kwargs):
    if not instance.pk and not hasattr(instance, _UNSAVED_FILEFIELD):
        setattr(instance, _UNSAVED_FILEFIELD, instance.image)
        instance.image = None

@receiver(post_save, sender=Image)
def save_file(sender, instance, created, **kwargs):
    if created and hasattr(instance, _UNSAVED_FILEFIELD):
        instance.image = getattr(instance, _UNSAVED_FILEFIELD)
        instance.save()        
        # delete it if you feel uncomfortable...
        # instance.__dict__.pop(_UNSAVED_FILEFIELD)

upload_path_handler看起来像

def upload_path_handler(instance, filename):
    import os.path
    fn, ext = os.path.splitext(filename)
    return "site_media/images/gallery/{id}{ext}".format(id=instance.pk, ext=ext)

如果该字段仅用于图片上传，我建议使用ImageField而不是FileField进行类型检查。此外，您可能希望规范化文件扩展名（由于mimetype而不需要），如

def normalize_ext(image_field):
    try:
        from PIL import Image
    except ImportError:
        import Image
    ext = Image.open(image_field).format
    if hasattr(image_field, 'seek') and callable(image_field.seek):
       image_field.seek(0)
    ext = ext.lower()
    if ext == 'jpeg':
        ext = 'jpg'
    return '.' + ext

Answer 3

在django 1.7中，提出的解决方案似乎对我没用，所以我编写了我的FileField子类以及一个删除旧文件的存储子类。

存储

class OverwriteFileSystemStorage(FileSystemStorage):
    def _save(self, name, content):
        self.delete(name)
        return super()._save(name, content)

    def get_available_name(self, name):
        return name

    def delete(self, name):
        super().delete(name)

        last_dir = os.path.dirname(self.path(name))

        while True:
            try:
                os.rmdir(last_dir)
            except OSError as e:
                if e.errno in {errno.ENOTEMPTY, errno.ENOENT}:
                    break

                raise e

            last_dir = os.path.dirname(last_dir)

的FileField：

def tweak_field_save(cls, field):
    field_defined_in_this_class = field.name in cls.__dict__ and field.name not in cls.__bases__[0].__dict__

    if field_defined_in_this_class:
        orig_save = cls.save

        if orig_save and callable(orig_save):
            assert isinstance(field.storage, OverwriteFileSystemStorage), "Using other storage than '{0}' may cause unexpected behavior.".format(OverwriteFileSystemStorage.__name__)

            def save(self, *args, **kwargs):
                if self.pk is None:
                    orig_save(self, *args, **kwargs)

                    field_file = getattr(self, field.name)

                    if field_file:
                        old_path = field_file.path
                        new_filename = field.generate_filename(self, os.path.basename(old_path))
                        new_path = field.storage.path(new_filename)
                        os.makedirs(os.path.dirname(new_path), exist_ok=True)
                        os.rename(old_path, new_path)
                        setattr(self, field.name, new_filename)

                    # for next save
                    if len(args) > 0:
                        args = tuple(v if k >= 2 else False for k, v in enumerate(args))

                    kwargs['force_insert'] = False
                    kwargs['force_update'] = False

                orig_save(self, *args, **kwargs)

            cls.save = save


def tweak_field_class(orig_cls):
    orig_init = orig_cls.__init__

    def __init__(self, *args, **kwargs):
        if 'storage' not in kwargs:
            kwargs['storage'] = OverwriteFileSystemStorage()

        if orig_init and callable(orig_init):
            orig_init(self, *args, **kwargs)

    orig_cls.__init__ = __init__

    orig_contribute_to_class = orig_cls.contribute_to_class

    def contribute_to_class(self, cls, name):
        if orig_contribute_to_class and callable(orig_contribute_to_class):
            orig_contribute_to_class(self, cls, name)

        tweak_field_save(cls, self)

    orig_cls.contribute_to_class = contribute_to_class

    return orig_cls


def tweak_file_class(orig_cls):
    """
    Overriding FieldFile.save method to remove the old associated file.
    I'm doing the same thing in OverwriteFileSystemStorage, but it works just when the names match.
    I probably want to preserve both methods if anyone calls Storage.save.
    """

    orig_save = orig_cls.save

    def new_save(self, name, content, save=True):
        self.delete(save=False)

        if orig_save and callable(orig_save):
            orig_save(self, name, content, save=save)

    new_save.__name__ = 'save'
    orig_cls.save = new_save

    return orig_cls


@tweak_file_class
class OverwriteFieldFile(models.FileField.attr_class):
    pass


@tweak_file_class
class OverwriteImageFieldFile(models.ImageField.attr_class):
    pass


@tweak_field_class
class RenamedFileField(models.FileField):
    attr_class = OverwriteFieldFile


@tweak_field_class
class RenamedImageField(models.ImageField):
    attr_class = OverwriteImageFieldFile

我的upload_to callable看起来像这样：

def user_image_path(instance, filename):
    name, ext = 'image', os.path.splitext(filename)[1]

    if instance.pk is not None:
        return os.path.join('users', os.path.join(str(instance.pk), name + ext))

    return os.path.join('users', '{0}_{1}{2}'.format(uuid1(), name, ext))

Answer 4

使用Louis's answer，这是处理模型中所有FileField的方法：

class MyModel(models.Model):

    file_field = models.FileField(upload_to=upload_to, blank=True, null=True)

    def save(self, *args, **kwargs):
        if self.id is None:
            saved = []
            for f in self.__class__._meta.get_fields():
                if isinstance(f, models.FileField):
                    saved.append((f.name, getattr(self, f.name)))
                    setattr(self, f.name, None)

            super(self.__class__, self).save(*args, **kwargs)

            for name, val in saved:
                setattr(self, name, val)
        super(self.__class__, self).save(*args, **kwargs)

Answer 5

对于Django 2.2，请遵循以下代码。

def save(self, *args, **kwargs):
    if self.pk is None:
        saved_image = self.image
        self.image = None
        super(Gallery, self).save(*args, **kwargs)
        self.image = saved_image
        if 'force_insert' in kwargs:
            kwargs.pop('force_insert')

    super(Gallery, self).save(*args, **kwargs)

将上述代码段添加到“类库”中。

P.S .：当您通过views.py保存时，这也适用于DRF。请注意，DRF需要第二个if（条件）。

使用当前模型ID的Django管理文件上传

5 个答案: