Finished GridFS Documentation

* Also made GridFS replace test pass

docs/django.rst

@@ -47,9 +47,10 @@ into you settings module::
 
 Storage
 =======
-With MongoEngine's support for GridFS via the FileField, it is useful to have a
-Django file storage backend that wraps this. The new storage module is called
-GridFSStorage. Using it is very similar to using the default FileSystemStorage.::
+With MongoEngine's support for GridFS via the :class:`~mongoengine.FileField`,
+it is useful to have a Django file storage backend that wraps this. The new
+storage module is called :class:`~mongoengine.django.GridFSStorage`. Using it
+is very similar to using the default FileSystemStorage.::
 
     fs = mongoengine.django.GridFSStorage()
 
@@ -57,29 +58,30 @@ GridFSStorage. Using it is very similar to using the default FileSystemStorage.:
 
 All of the `Django Storage API methods
 <http://docs.djangoproject.com/en/dev/ref/files/storage/>`_ have been
-implemented except ``path()``. If the filename provided already exists, an
+implemented except :func:`path`. If the filename provided already exists, an
 underscore and a number (before # the file extension, if one exists) will be
 appended to the filename until the generated filename doesn't exist. The
-``save()`` method will return the new filename.::
+:func:`save` method will return the new filename.::
 
-    > fs.exists('hello.txt')
+    >>> fs.exists('hello.txt')
     True
-    > fs.open('hello.txt').read()
+    >>> fs.open('hello.txt').read()
     'Hello, World!'
-    > fs.size('hello.txt')
+    >>> fs.size('hello.txt')
     13
-    > fs.url('hello.txt')
+    >>> fs.url('hello.txt')
     'http://your_media_url/hello.txt'
-    > fs.open('hello.txt').name
+    >>> fs.open('hello.txt').name
     'hello.txt'
-    > fs.listdir()
+    >>> fs.listdir()
     ([], [u'hello.txt'])
 
-All files will be saved and retrieved in GridFS via the ``FileDocument`` document,
-allowing easy access to the files without the GridFSStorage backend.::
+All files will be saved and retrieved in GridFS via the :class::`FileDocument`
+document, allowing easy access to the files without the GridFSStorage
+backend.::
 
-    > from mongoengine.django.storage import FileDocument
-    > FileDocument.objects()
+    >>> from mongoengine.django.storage import FileDocument
+    >>> FileDocument.objects()
     [<FileDocument: FileDocument object>]
 
 .. versionadded:: 0.4

docs/guide/gridfs.rst

@@ -1,11 +1,17 @@
 ======
 GridFS
 ======
+
+.. versionadded:: 0.4
+
+Writing
+-------
+
 GridFS support comes in the form of the :class:`~mongoengine.FileField` field
 object. This field acts as a file-like object and provides a couple of
-different ways of inserting and retrieving data. Metadata such as content-type
-can also be stored alongside the stored files. In the following example, an
-document is created to store details about animals, including a photo:
+different ways of inserting and retrieving data. Arbitrary metadata such as
+content type can also be stored alongside the files. In the following example,
+a document is created to store details about animals, including a photo::
 
     class Animal(Document):
         genus = StringField()
@@ -14,13 +20,64 @@ document is created to store details about animals, including a photo:
 
     marmot = Animal('Marmota', 'Sciuridae')
 
-    marmot_photo = open('marmot.jpg')   # Retrieve a photo from disk
+    marmot_photo = open('marmot.jpg', 'r')      # Retrieve a photo from disk
     marmot.photo = marmot_photo                 # Store the photo in the document
+    marmot.photo.content_type = 'image/jpeg'    # Store metadata
 
     marmot.save()
 
-So adding file data to a document is as easy as adding data to any other 
+Another way of writing to a :class:`~mongoengine.FileField` is to use the
+:func:`put` method. This allows for metadata to be stored in the same call as
+the file::
 
-.. versionadded:: 0.4
+    marmot.photo.put(marmot_photo, content_type='image/jpeg')
+
+    marmot.save()
+
+Retrieval
+---------
+
+So using the :class:`~mongoengine.FileField` is just like using any other
+field. The file can also be retrieved just as easily::
+
+    marmot = Animal.objects('Marmota').first()
+    photo = marmot.photo.read()
+    content_type = marmot.photo.content_type
+
+Streaming
+---------
+
+Streaming data into a :class:`~mongoengine.FileField` is achieved in a
+slightly different manner.  First, a new file must be created by calling the
+:func:`new_file` method. Data can then be written using :func:`write`::
+
+    marmot.photo.new_file()
+    marmot.photo.write('some_image_data')
+    marmot.photo.write('some_more_image_data')
+    marmot.photo.close()
+
+    marmot.photo.save()
+
+Deletion
+--------
+
+Deleting stored files is achieved with the :func:`delete` method::
+
+    marmot.photo.delete()
+
+.. note::
+    The FileField in a Document actually only stores the ID of a file in a
+    separate GridFS collection. This means that deleting a document
+    with a defined FileField does not actually delete the file. You must be
+    careful to delete any files in a Document as above before deleting the
+    Document itself.
 
 
+Replacing files
+---------------
+
+Files can be replaced with the :func:`replace` method. This works just like
+the :func:`put` method so even metadata can (and should) be replaced::
+
+    another_marmot = open('another_marmot.png', 'r')
+    marmot.photo.replace(another_marmot, content_type='image/png')

mongoengine/fields.py

@@ -586,14 +586,14 @@ class GridFSProxy(object):
 
     def put(self, file, **kwargs):
         if self.grid_id:
-            raise GridFSError('This document alreay has a file. Either delete '
+            raise GridFSError('This document already has a file. Either delete '
                               'it or call replace to overwrite it')
         self.grid_id = self.fs.put(file, **kwargs)
 
     def write(self, string):
         if self.grid_id:
             if not self.newfile:
-                raise GridFSError('This document alreay has a file. Either '
+                raise GridFSError('This document already has a file. Either '
                                   'delete it or call replace to overwrite it')
         else:
             self.new_file()
@@ -622,6 +622,7 @@ class GridFSProxy(object):
 
     def replace(self, file, **kwargs):
         self.delete()
+        self.grid_id = None
         self.put(file, **kwargs)
 
     def close(self):