Can Django Models Utilize Custom Properties to Skip Image Resizing on Non-Image Field Changes?

Skipping Image Resizing on Non-Image Field Changes in Django

When saving a Django model, it can be necessary to perform certain actions only when specific fields are changed. In cases where an image field is present, users might want to resize the image when it's uploaded or updated but skip the process when only other fields, such as the description, are modified.

Problem:

In the provided Django model, the save() method performs image rescaling regardless of whether the image itself has been changed. This approach is inefficient and can result in unnecessary computation.

Solution Using Custom Property and Setter:

One solution is to introduce a custom property with a setter to control image resizing. Here's an example:

<code class="python">class Model(model.Model):
    _image = models.ImageField(upload_to='folder')
    thumb = models.ImageField(upload_to='folder')
    description = models.CharField()

    def set_image(self, val):
        self._image = val
        self._image_changed = True

        if self._image_changed:
            # Perform image rescaling logic here, if necessary
            pass

    def get_image(self):
        return self._image

    image = property(get_image, set_image)

    def save(self, *args, **kwargs):
        if getattr(self, '_image_changed', True):
            super(Model, self).save(*args, **kwargs)
            # Perform image rescaling logic here (if implemented in `set_image`)</code>

This approach utilizes a custom property named image that serves as a wrapper around the actual image field named _image. The set_image() method is used to assign a new value to the _image field and also to set the _image_changed flag to True. The _image_changed flag is used to determine whether image rescaling is necessary.

In the save() method, the program checks the value of _image_changed. If it's True, it assumes that the image field has been changed and proceeds with the image rescaling logic. If _image_changed is False, it means that the image field has not been changed, and the program skips the image rescaling step.

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