Django Templates — passing value of a variable in a template to templatetags filter

Question

name class an id, a first & a last attributes

In my view.py, I fetch a name object from the database and pass it into the index.html template.

In my templagetags/my_tags.py, I have a filter my_private_tag(value, arg) that takes value and an arg. It appends the arg to the value and returns the result.

def my_private_tag(value, arg):
  return value + ' ' + arg

In my index.html tag I need to do the following.

{% if name %}

  # to display 
  # John says hello
  {{name.first | my_private_tag:"says hello"}

  # Johns student id = id_value
  {{name.first | my_private_tag:"????????"}

  # Johns student id = id_value, lastname = lastname_value
  {{name.first | my_private_tag:"????????"}

{% endif %}

Where:

id_value = name.id & lastname_value = name.last

Please fill in the ???????? if you can.

Answer 1

Instead of implementing your own filter for this. Why not do it this way:

{{name.first }} says hello
{{name.first }}'s student id = {{ name.id }}

It is much more readable. And this is how you are supposed to use templates anyway.

If you still want to use a custom filter for this, you can probably pass the variable like this:

{{name.first|my_private_tag:name.id}}

Answer 2

If the filter only gets two strings, it won't have access to the original name object, so there's no way to get the ID.

I think you're headed the wrong direction by wanting to do this with a filter when you can use the existing tags to get the result you want. But, for the sake of argument, let's say that you could get

Johns student id = 47, lastname = Doe

from the filter. How would you do it? First, you'd have to pass the name object to the filter

{{name|my_private_tag:"??????"}}

The code for the filter then becomes

return name.first_name + "s student id = " + name.id + ", lastname = " + name.last_name

Notice that you're not using the argument. If you wanted your filter to return different things depending on the argument, then add conditional logic and off you go.