Links Framework

Widgy core also provides a linking framework that allows any model to point to any other model without really knowing which models are available for linking. This is the mechanism by which Page Builder’s Button can link to Widgy Mezzanine’s WidgyPage without even knowing that WidgyPage exists. There are two components to the links framework, LinkField and the link registry.

Model Field

class widgy.models.links.LinkField

LinkField is a subclass of django.contrib.contenttypes.generic.GenericForeignKey. If you want to add a link to any model, you can just add a LinkField to it.

from django.db import models
from widgy.models import links

class MyModel(models.Model):
    title = models.Charfield(max_length=255)
    link = links.LinkField()

LinkField will automatically add the two required fields for GenericForeignKey, the ContentType ForeignKey and the PositiveIntegerField. If you need to override this, you can pass in the ct_field and fk_field options that GenericForeignKey takes.

Note

Unfortunately, because Django currently lacks support for composite fields, if you need to display the LinkField in a form, there are a couple of things you need to do.

1. Your Form class needs to mixin the LinkFormMixin.
2. You need to explicitly define a LinkFormField on your Form class.

Hopefully in future iterations of Django, these steps will be obsoleted.

Registry

If you want to expose your model to the link framework to allow things to link to it, you need to do two things.

1. You need to register your model with the links registry.

   from django.db import models
   from widgy.models import links
   
   class Blog(models.Model):
       # ...
   
   links.register(Blog)
   

   The register() function also works as a class decorator.

   from django.db import models
   from widgy.models import links
   
   @links.register
   class Blog(models.Model):
       # ...
   

2. You need to make sure that your model defines a get_absolute_url method.