Improved signals documentation and some typo fixes.

docs/guide/defining-documents.rst

@@ -403,7 +403,7 @@ either a single field name, or a list or tuple of field names::
 Skipping Document validation on save
 ------------------------------------
 You can also skip the whole document validation process by setting
-``validate=False`` when caling the :meth:`~mongoengine.document.Document.save`
+``validate=False`` when calling the :meth:`~mongoengine.document.Document.save`
 method::
 
     class Recipient(Document):

docs/guide/signals.rst

@@ -1,5 +1,6 @@
 .. _signals:
 
+=======
 Signals
 =======
 
@@ -7,32 +8,92 @@ Signals
 
 .. note::
 
-  Signal support is provided by the excellent `blinker`_ library and
-  will gracefully fall back if it is not available.
+  Signal support is provided by the excellent `blinker`_ library. If you wish
+  to enable signal support this library must be installed, though it is not
+  required for MongoEngine to function.
+
+Overview
+--------
+
+Signals are found within the :module:`~mongoengine.signals` module.  Unless
+specified signals receive no additional arguments beyond the `sender` class and
+`document` instance.  Post-signals are only called if there were no exceptions
+raised during the processing of their related function.
+
+Available signals include:
+
+`pre_init`
+  Called during the creation of a new :class:`~mongoengine.Document` or
+  :class:`~mongoengine.EmbeddedDocument` instance, after the constructor
+  arguments have been collected but before any additional processing has been
+  done to them.  (I.e. assignment of default values.)  Handlers for this signal
+  are passed the dictionary of arguments using the `values` keyword argument
+  and may modify this dictionary prior to returning.
+
+`post_init`
+  Called after all processing of a new :class:`~mongoengine.Document` or
+  :class:`~mongoengine.EmbeddedDocument` instance has been completed.
+
+`pre_save`
+  Called within :meth:`~mongoengine.document.Document.save` prior to performing
+  any actions.
+
+`post_save`
+  Called within :meth:`~mongoengine.document.Document.save` after all actions
+  (validation, insert/update, cascades, clearing dirty flags) have completed
+  successfully.  Passed the additional boolean keyword argument `created` to
+  indicate if the save was an insert or an update.
+
+`pre_delete`
+  Called within :meth:`~mongoengine.document.Document.delete` prior to
+  attempting the delete operation.
+
+`post_delete`
+  Called within :meth:`~mongoengine.document.Document.delete` upon successful
+  deletion of the record.
+
+`pre_bulk_insert`
+  Called after validation of the documents to insert, but prior to any data
+  being written. In this case, the `document` argument is replaced by a
+  `documents` argument representing the list of documents being inserted.
+
+`post_bulk_insert`
+  Called after a successful bulk insert operation.  As per `pre_bulk_insert`,
+  the `document` argument is omitted and replaced with a `documents` argument.
+  An additional boolean argument, `loaded`, identifies the contents of
+  `documents` as either :class:`~mongoengine.Document` instances when `True` or
+  simply a list of primary key values for the inserted records if `False`.
 
 
-The following document signals exist in MongoEngine and are pretty self-explanatory:
+Attaching Events
+----------------
 
-  * `mongoengine.signals.pre_init`
-  * `mongoengine.signals.post_init`
-  * `mongoengine.signals.pre_save`
-  * `mongoengine.signals.post_save`
-  * `mongoengine.signals.pre_delete`
-  * `mongoengine.signals.post_delete`
-  * `mongoengine.signals.pre_bulk_insert`
-  * `mongoengine.signals.post_bulk_insert`
+After writing a handler function like the following::
 
-Example usage::
+    import logging
+    from datetime import datetime
     
     from mongoengine import *
     from mongoengine import signals
     
+    def update_modified(sender, document):
+        document.modified = datetime.utcnow()
+
+You attach the event handler to your :class:`~mongoengine.Document` or
+:class:`~mongoengine.EmbeddedDocument` subclass::
+
+    class Record(Document):
+        modified = DateTimeField()
+    
+    signals.pre_save.connect(update_modified)
+
+While this is not the most elaborate document model, it does demonstrate the
+concepts involved.  As a more complete demonstration you can also define your
+handlers within your subclass::
+
     class Author(Document):
         name = StringField()
         
-        def __unicode__(self):
-            return self.name
-
         @classmethod
         def pre_save(cls, sender, document, **kwargs):
             logging.debug("Pre Save: %s" % document.name)
@@ -49,12 +110,40 @@ Example usage::
     signals.pre_save.connect(Author.pre_save, sender=Author)
     signals.post_save.connect(Author.post_save, sender=Author)
 
+Finally, you can also use this small decorator to quickly create a number of
+signals and attach them to your :class:`~mongoengine.Document` or
+:class:`~mongoengine.EmbeddedDocument` subclasses as class decorators::
 
-ReferenceFields and signals
+    def handler(event):
+        """Signal decorator to allow use of callback functions as class decorators."""
+        
+        def decorator(fn):
+            def apply(cls):
+                event.connect(fn, sender=cls)
+                return cls
+            
+            fn.apply = apply
+            return fn
+        
+        return decorator
+
+Using the first example of updating a modification time the code is now much
+cleaner looking while still allowing manual execution of the callback::
+
+    @handler(signals.pre_save)
+    def update_modified(sender, document):
+        document.modified = datetime.utcnow()
+    
+    @update_modified.apply
+    class Record(Document):
+        modified = DateTimeField()
+
+
+ReferenceFields and Signals
 ---------------------------
 
 Currently `reverse_delete_rules` do not trigger signals on the other part of
-the relationship.  If this is required you must manually handled the
+the relationship.  If this is required you must manually handle the
 reverse deletion.
 
 .. _blinker: http://pypi.python.org/pypi/blinker