Django：在其他应用程序中使用 ImageFields？

Question

我有一些上传图片的应用程序。现在几乎相同的代码在每个应用程序中多次出现，我希望从名为 images 的应用程序加载图像。是否可以连接其他应用以便它们使用 app1[images] ShareImage 类的 ImageFields？

如果没有，我该如何使用 image_resize 方法和两个@receiver 函数，以便它们可以被多个应用程序使用，而我只有一个代码：

我以前尝试过遗传，但我无法摆脱它。

我还尝试通过 Import 将 ImageFields 导入另一个类。

应用程序1：

import os

from io import BytesIO
from PIL import Image
from django.db import models
from django.dispatch import receiver
from django.core.files.base import ContentFile
from .storage import OverwriteStorage


class ShareImage(models.Model):
    image = models.ImageField(
        upload_to='images/',
        verbose_name='Bild',
        storage=OverwriteStorage(),
    )

    thumbnail = models.ImageField(
        upload_to='images/',
        editable=False,
        storage=OverwriteStorage(),
    )

    def save(self, *args, **kwargs):
        if not os.path.exists(self.image.path) and not self.images_resize():
            raise Exception('Error: Thumbnail not created')

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

    def images_resize(self):
        size = (288, 162)

        image = Image.open(self.image)
        image.thumbnail(size, Image.ANTIALIAS)

        name, extension = os.path.splitext(self.image.name)
        # to prevent django from creating new folders incorrectly
        name = os.path.basename(name)
        extension = extension.lower()
        file_name = name + '_thumbnail' + extension

        if extension in ['.jpg', '.jpeg']:
            file_extension = 'JPEG'
        elif extension == '.png':
            file_extension = 'PNG'
        elif extension == '.gif':
            file_extension = 'GIF'
        else:
            raise Exception('Error: Files extension not supported')

        temp = BytesIO()
        image.save(temp, file_extension)
        temp.seek(0)

        if not os.path.exists(self.image.path):
            self.thumbnail.save(
                file_name, ContentFile(temp.read()), save=False
            )
            return True


@receiver(models.signals.post_delete, sender=ShareImage)
def auto_delete_images_on_delete(instance, **kwargs):
    if instance.image:
        if os.path.isfile(instance.image.path):
            os.remove(instance.image.path)

    if instance.thumbnail:
        if os.path.isfile(instance.thumbnail.path):
            os.remove(instance.thumbnail.path)


@receiver(models.signals.pre_save, sender=ShareImage)
def auto_delete_images_on_change(instance, **kwargs):
    if not instance.pk:
        return False

    try:
        old_image = ShareImage.objects.get(pk=instance.pk).image
        old_thumb = ShareImage.objects.get(pk=instance.pk).thumbnail
    except ShareImage.DoesNotExist:
        return False

    new_image = instance.image
    new_thumb = instance.thumbnail

    if old_image != new_image:
        if os.path.isfile(old_image.path):
            os.remove(old_image.path)

    if old_thumb != new_thumb:
        if os.path.isfile(old_thumb.path):
            os.remove(old_thumb.path)

示例 app2：

import os

from io import BytesIO
from PIL import Image
from django.db import models
from django.dispatch import receiver
from django.core.files.base import ContentFile
from .storage import OverwriteStorage


class Logo(models.Model):
    title = models.CharField(max_length=100, unique=True, verbose_name='Titel')
    slug = models.SlugField(max_length=100, unique=True)
    created = models.DateTimeField(auto_now_add=True, verbose_name='Erstellt')
    updated = models.DateTimeField(auto_now=True, verbose_name='Aktualisiert')
    image = models.ImageField(upload_to='website/header/images/',
                              verbose_name='Bild', storage=OverwriteStorage())
    thumbnail = models.ImageField(upload_to='website/header/images/',
                                  editable=False, storage=OverwriteStorage())
    public = models.BooleanField(verbose_name='Öffentlich')

    class Meta:
        ordering = ['-updated']
        verbose_name = 'Logo'
        verbose_name_plural = 'Logos'

    def __str__(self):
        return self.title

Answer 1

您可以将ShareImage 设为abstract model，并从中继承其他类。例如：

class ShareImage(models.Model):
   ...
   class Meta:
        abstract = True


class Logo(ShareImage):
   ...

这样，Logo 类将具有字段image 和thumbnail。但这不会触发信号。

另外，还有另一种方法，将ShareImage 作为OneToOneField 添加到Logo：

class Logo(models.Model):
    image = models.OneToOneField(ShareImage)
    ...

    def delete(self, *args, **kwargs):
        self.image.delete()
        return super(Logo, self).delete(*args, **kwargs)

这样，ShareImage 的删除应该会触发这些信号。