Base64 file handling for django-tastypie

b64field.py

import base64
import os
from tastypie.fields import FileField
from django.core.files.uploadedfile import SimpleUploadedFile

class Base64FileField(FileField):
    """
    A django-tastypie field for handling file-uploads through raw post data.
    It uses base64 for en-/decoding the contents of the file.
    Usage:

    class MyResource(ModelResource):
        file_field = Base64FileField("file_field")
        
        class Meta:
            queryset = ModelWithFileField.objects.all()

    In the case of multipart for submission, it would also pass the filename.
    By using a raw post data stream, we have to pass the filename within our
    file_field structure:

    file_field = {
        "name": "myfile.png",
        "file": "longbas64encodedstring",
        "content_type": "image/png" # on hydrate optional
    }
    """
    def dehydrate(self, bundle):
        if not bundle.data.has_key(self.instance_name) and hasattr(bundle.obj, self.instance_name):
            file_field = getattr(bundle.obj, self.instance_name)
            if file_field:
                try:
                    content_type, encoding = mimetypes.guess_type(file_field.file.name)
                    b64 = open(file_field.file.name, "rb").read().encode("base64")
                    ret = {
                        "name": os.path.basename(file_field.file.name),
                        "file": b64,
                        "content-type": content_type or "application/octet-stream"
                    }
                    return ret
                except:
                    pass
        return None

    def hydrate(self, obj):
        value = super(FileField, self).hydrate(obj)
        if value:
            value = SimpleUploadedFile(value["name"], base64.b64decode(value["file"]), getattr(value, "content_type", "application/octet-stream"))
        return value

An alternative for passing the filename would be to use a data uri http://tools.ietf.org/html/rfc2397:

data:image/png;filename="myfile.png";base64,asfwegheghe==

That field saves file to database or disk?

If you POST/PUT the Base64 file string to a tastypie-resource that is using this Base64FileField it'll turn the Base64 string into an UploadedFile object that then can be used by model.save directly. Depending on your storage-backend of your model's file field it then either saves the file to your disk+reference string to your db (default) or to another location which is defined in your storage class.

Ah i see now, very nice thanks :)

Anyone can provide some more info on how to use this solution?
I have a form with a file field in forms.py and then a model with a fiel field in models.py.
Do I need to create another file with the above class, and then how do I use it with the form or with the model?
Is the right thing to do is to use Base64FileField instead of FileField in my form or in my model?
And lastly when does dehydrate function actually get called?
Here is the section from forms.py:

class DocumentUploadForm(forms.Form):
document_name = forms.CharField(max_length=30, required=False)
description = forms.CharField(widget=forms.Textarea(attrs={'cols': 60, 'rows': 4}), required=False)
docfile = forms.FileField(label='Select a file', help_text='max. 40 megabytes')

And here is the section from models.py:
class Document(models.Model):
document_name = models.CharField(max_length=30, null=True)
description = models.TextField(null=True)
document = models.FileField(upload_to='documents/%Y/%m/%d')

Thanks,
Moshe

Hey klipstein, thank you for this! In the current tastypie version (django-tastypie==0.9.15) you have to make a little change for this to work, otherwise you'll get an "dehydrate() got an unexpected keyword argument 'for_list'" exception:

change:
def dehydrate(self, bundle):

to:
def dehydrate(self, bundle, for_list):

Also missing:

import mimetypes

Any hints on checking resolution of the incoming file when using this for an image?