Signals in DMP

DMP sends several custom signals through the Django signal dispatcher. The purpose is to allow you to hook into the router’s processing and respond to events that occur in DMP.

Before going further with this section’s examples, be sure to read the standard Django signal documentation. DMP signals are simply additional signals in the same dispatching system, so the following examples should be easy to understand once you know how Django dispatches signals.

Available Signals

dmp_signal_pre_process_request

Triggered just before DMP calls a view’s process_request() method.

dmp_signal_post_process_request

Triggered just after a view’s process_request() method returns.

dmp_signal_pre_render_template

Triggered just before DMP renders a Mako template.

dmp_signal_post_render_template

Triggered just after DMP renders a Mako template.

dmp_signal_redirect_exception

Triggered when a RedirectException is encountered in the DMP controller.

dmp_signal_internal_redirect_exception

Triggered when an InternalRedirectException is encountered in the DMP controller.

dmp_signal_register_app

Triggered just after the DMP template engine registers an app as a DMP app (once per app at server start).

See the function documentation in signals.py for more information about each signal and its kwargs.

Enabling DMP Signals

Be sure your settings.py file has the following in it:

TEMPLATES = [
    {
        'NAME': 'django_mako_plus',
        'BACKEND': 'django_mako_plus.MakoTemplates',
        'OPTIONS': {
            'SIGNALS': True,
            ...
        }
    }
]

Signal Receivers

The following creates two receivers. The first is called just before the view’s process_request function is called. The second is called just before DMP renders .html templates.

from django.dispatch import receiver
from django_mako_plus import signals, get_template_loader

@receiver(signals.dmp_signal_pre_process_request)
def pre_process_request(sender, request, view_args, view_kwargs, **kwargs):
    print('>>> process_request signal received!')

@receiver(signals.dmp_signal_pre_render_template)
def pre_render_template(sender, request, context, template, **kwargs):
    print('>>> render_template signal received!')
    # let's return a different template to be used - DMP will use this instead of kwargs['template']
    tlookup = get_template_loader('myapp')
    template = tlookup.get_template('different.html')

The above code should be in a code file that is called during Django initialization, such as apps.py.