Re: Migrations and FileField storage

Hi Nico,

I had the same problem when I was using this storage object:

photoStorage = FileSystemStorage(location=os.path.join(settings.MEDIA_ROOT, 'photos/original'), base_url='/photos/original')

class Photo(models.Model):
    image = models.ImageField(storage=photoStorage)

The "location" argument ends up being serialized, which makes the migrations dependent on MEDIA_ROOT. To fix the problem I wrote my own subclass of FileSystemStorage:

@deconstructible

class PhotoFileSystemStorage(FileSystemStorage):

def __init__(self, photoPath):

self.photoPath = photoPath

super(PhotoFileSystemStorage,self).__init__(location=os.path.join(settings.MEDIA_ROOT, self.photoPath), base_url=self.photoPath)

def __eq__(self, other):

       return self.photoPath == other.photoPath

photoStorage = PhotoFileSystemStorage('photos/original')

When an instance of PhotoFileSystemStorage is serialized it just writes out self.photoPath, which does not depend on MEDIA_ROOT. After implementing this, the migration looks like this:

class Migration(migrations.Migration):

    dependencies = [

        ...

    ]

    operations = [

        migrations.AlterField(

            model_name='photo',

            name='image',

            field=models.ImageField(storage=myapp.models.PhotoFileSystemStorage(b'photos/original')),

        ),

    ]

You can see it does not depend on MEDIA_ROOT and won't be different if you move the project around or deploy it.

The django docs on this are here: https://docs.djangoproject.com/en/1.8/topics/migrations/

Hope this helps.


Steve

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