Django Template Tags and Filters Custom Filters
Example
Filters allows you to apply a function to a variable. This function may take 0 or 1 argument. Here is the syntax:
{{ variable|filter_name }}
{{ variable|filter_name:argument }}
Filters can be chained so this is perfectly valid:
{{ variable|filter_name:argument|another_filter }}
If translated to python the above line would give something like this:
print(another_filter(filter_name(variable, argument)))
In this example, we will write a custom filter verbose_name that applies to a Model (instance or class) or a QuerySet. It will return the verbose name of a model, or its verbose name plural if the argument is set to True.
@register.filter
def verbose_name(model, plural=False):
"""Return the verbose name of a model.
`model` can be either:
- a Model class
- a Model instance
- a QuerySet
- any object refering to a model through a `model` attribute.
Usage:
- Get the verbose name of an object
{{ object|verbose_name }}
- Get the plural verbose name of an object from a QuerySet
{{ objects_list|verbose_name:True }}
"""
if not hasattr(model, '_meta'):
# handle the case of a QuerySet (among others)
model = model.model
opts = model._meta
if plural:
return opts.verbose_name_plural
else:
return opts.verbose_name
