"""
Below is an example of some signals I use in Django to update denormalized counts and to Tweet out
automatically when certain records are created.
"""

def channel_post_save(sender, instance, created, **kwargs):
    """
    Increment the number of channels in the category. A corollary `channel_post_delete` would be
    created as well to reverse this change out. I attach my signals in my models.py and save
    them in signals.py.
    """
    if created is True:
        instance.category.channels = instance.category.channels + 1
        instance.category.save()

        # Obviously we shouldn't tweet if we're in DEBUG mode. Also, we don't
        # tweet out our own channel creations. Just other 3rd party channels.
        if settings.DEBUG is True and instance.name[:5] != "TMTTI":
            msg = 'Just added %s (%s) to our index!'
            api = twitter.Api(username="your_username", password="secret")
            api.PostUpdate(msg % (instance.name, instance.site))

def url_post_save(sender, instance, created, **kwargs):
    """
    Increment the number of URLs in both the category and in the channel
    """
    if created is True:
        instance.channel.category.urls = instance.channel.category.urls + 1
        instance.channel.category.save()

        instance.channel.urls = instance.channel.urls + 1
        instance.channel.save()