Social Networking - MongoDB Applied Design Patterns - page 156

Creating a New Post

Creating a new post fills out the content-creation activities on a social network:

from from datetime datetime import import datetime

def def post ( user , dest_user , type , detail , circles ):

ts = datetime . utcnow ()
month = ts . strfime ( '%Y%m' )
post = {
'ts' : ts ,
'by' : { id : user [ 'id' ], name : user [ 'name' ] },
'circles' : circles ,
'type' : type ,
'detail' : detail ,
'comments' : [] }
# Update global post collection
db . social . post . insert ( post )
# Copy to dest user's wall
iif user [ 'id' ] not

not iin dest_user [ 'blocked' ]:
append_post ( db . social . wall , [ dest_user [ 'id' ]], month , post )
# Copy to followers' news feeds
iif circles == [ '*public*' ]:
dest_userids = set ( user [ 'followers' ] . keys ())

else else :

dest_userids = set ()
iif circles == [ '*circles*' ]:
circles = user [ 'circles' ] . keys ()

for circle iin circles :
dest_userids . update ( user [ 'circles' ][ circle ])
append_post ( db . social . news , dest_userids , month , post )

for

The basic sequence of operations in this code is as follows:

1. The post is first saved into the “system of record,” the social.post collection.

2. The recipient's wall is updated with the post.

3. The news feeds of everyone who is circled in the post is updated with the post.

Updating a particular wall or group of news feeds is then accomplished using the ap-
pend_post function: