As the primary key (id) may not be available if the model instance was not saved to the database yet, I wrote my FileField subclasses which move the file on model save, and a storage subclass which removes the old files.
Storage:
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)
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
and my upload_to callables look like this:
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))
instance's attribute before it is saved. I was wrong, those Car attributes have been bounded toinstance, yet haven't been saved in database – Brit