* added 'OverwriteStorage()' to overwrite previous uploaded files

* overwrite 'save' method to delete previous uploaded files

2 files changed, 87 insertions, 1 deletions

diff --git a/account/extra.py b/account/extra.py
index c247b8f..6ff19b2 100644
--- a/account/extra.py
+++ b/account/extra.py
@@ -6,9 +6,14 @@ Extra models for app account
 
 from django.db import models
 from django import forms
+from django.core.files.storage import FileSystemStorage
+from django.conf import settings
 from django.template.defaultfilters import filesizeformat
 from django.utils.translation import ugettext_lazy as _
 
+import os
+
+
 class ContentTypeRestrictedFileField(models.FileField):
     """
     Same as FileField, but you can specify:
@@ -48,3 +53,36 @@ class ContentTypeRestrictedFileField(models.FileField):
         #
         return data
 
+
+### OverwriteStorage ###
+class OverwriteStorage(FileSystemStorage):
+    """
+    overwrite original file before store the new one
+    """
+    def get_available_name(self, name):
+        """
+        Returns a filename that's free on the target storage system,
+        and available for new content to be written to.
+        Ref: http://djangosnippets.org/snippets/976/
+
+        This file storage solves overwrite on upload problem. Another
+        proposed solution was to override the save method on the model
+        like so (from https://code.djangoproject.com/ticket/11663):
+
+        def save(self, *args, **kwargs):
+            try:
+                this = MyModelName.objects.get(id=self.id)
+                if this.MyImageFieldName != self.MyImageFieldName:
+                    this.MyImageFieldName.delete()
+            except: pass
+            super(MyModelName, self).save(*args, **kwargs)
+        """
+        # If the filename already exists,
+        # remove it as if it was a true file system
+        if self.exists(name):
+            filepath = os.path.join(settings.MEDIA_ROOT, name)
+            if os.path.isfile(filepath):
+                os.remove(filepath)
+        return name
+
+
diff --git a/account/models.py b/account/models.py
index 257477d..cb806da 100644
--- a/account/models.py
+++ b/account/models.py
@@ -6,12 +6,14 @@
 
 from django.db import models
 from django.contrib.auth.models import User
+from django.db.models.fields.files import FieldFile
 from django.conf import settings
 from django.utils.translation import ugettext_lazy as _
 
+from django.db.models.signals import pre_delete
 from registration.signals import user_registered
 
-from account.extra import ContentTypeRestrictedFileField
+from account.extra import ContentTypeRestrictedFileField, OverwriteStorage
 
 
 ###### account models ######
@@ -68,6 +70,7 @@ class UserProfile(models.Model):
     # transcript: needed if undergraudate (junior and below)
     transcript = ContentTypeRestrictedFileField(upload_to=lambda instance, filename: u'account/{0}/{1}'.format(instance.user.username, filename),
             verbose_name=_("Transcript"), blank=True, null=True,
+            storage=OverwriteStorage(),
             content_types=settings.ALLOWED_CONTENT_TYPES,
             max_upload_size=settings.ALLOWED_MAX_UPLOAD_SIZE)
     # supplement: record additional information
@@ -85,6 +88,18 @@ class UserProfile(models.Model):
     def __unicode__(self):
         return u'UserProfile for %s' % self.user.username
 
+    def save(self, *args, **kwargs):
+        """
+        overwrite the original save method to delete old file
+        """
+        old_obj = type(self).objects.get(pk=self.pk)
+        result = super(UserProfile, self).save(*args, **kwargs)
+        # if the path is the same, the file is overwritten already
+        if old_obj.transcript.path != self.transcript.path:
+            old_obj.transcript.delete(save=False)
+        #
+        return result
+
     def is_transcript_required(self):
         """
         if 'identify' is UG (undergraduate junior and below); then
@@ -152,6 +167,7 @@ class UserFile(models.Model):
     description = models.TextField(_("Description"), blank=True)
     file = ContentTypeRestrictedFileField(upload_to=lambda instance, filename: u'account/{0}/{1}'.format(instance.user.username, filename),
             verbose_name=_("File"),
+            storage = OverwriteStorage(),
             content_types=settings.ALLOWED_CONTENT_TYPES,
             max_upload_size=settings.ALLOWED_MAX_UPLOAD_SIZE)
     created_at = models.DateTimeField(_("Created time"),
@@ -166,6 +182,18 @@ class UserFile(models.Model):
     def __unicode__(self):
         return u'UserFile of %s: %s' % (self.user.username, self.title)
 
+    def save(self, *args, **kwargs):
+        """
+        overwrite the original save method to delete old file
+        """
+        old_obj = type(self).objects.get(pk=self.pk)
+        result = super(UserFile, self).save(*args, **kwargs)
+        # if the path is the same, the file is overwritten already
+        if old_obj.file.path != self.file.path:
+            old_obj.file.delete(save=False)
+        #
+        return result
+
 
 ###### signal callback ######
 def user_registered_callback(sender, user, request, **kwargs):
@@ -185,3 +213,23 @@ def user_registered_callback(sender, user, request, **kwargs):
 user_registered.connect(user_registered_callback)
 
 
+### delete files associated with model FileField
+# Pre-delete signal function for deleting files a model
+# https://djangosnippets.org/snippets/2820/
+def file_cleanup(sender, instance, *args, **kwargs):
+    """
+    Deletes the file(s) associated with a model instance. The model
+    is not saved after deletion of the file(s) since this is meant
+    to be used with the pre_delete signal.
+    """
+    for field_name, _ in instance.__dict__.iteritems():
+        field = getattr(instance, field_name)
+        if (issubclass(field.__class__, FieldFile) and field.name):
+            # pass False so FileField does not save the model
+            field.delete(save=False)
+
+### connect to signal and sender
+pre_delete.connect(file_cleanup, sender=UserProfile)
+pre_delete.connect(file_cleanup, sender=UserFile)
+
+