Question

I defined one custom tag {% get_user user_id %} which catch user’s id and return user object through variable user_obj: {{ user_obj.email }}, {{ user_obj.name }}, {{ user_obj.photo.url }} and so on.

And it works fine. Next I defined tag {% get_user_items user %} which get user object and returns user’s photo url through variable user_photo: {{ user_photo }}.

I want to make interaction between this 2 custom tags. It means smth like that:

{% load user_tags %}
{% get_user 1 %}
{{ user_obj }} // returns unicode string as expected
{% get_user_items user_obj %}
{{ user_photo }}

As I understand tag ‘get_user_items’ must get a user object through variable user_obj, but no – it gets from variable user_obj the usual string ‘user_obj’, not object!!!

How to fix this? What am I doing wrong??? How can I transmit value from variable {{ user_obj }} to tag {% get_user_items %} directly?

Thanks for your answers in advance!!!

Answer 1

You have to resolve the string as a variable using the context. See discussion on passing template variables to tags in the Django docs

class FormatTimeNode(template.Node):
    def __init__(self, date_to_be_formatted, format_string):
        self.date_to_be_formatted = template.Variable(date_to_be_formatted)
        self.format_string = format_string

    def render(self, context):
        try:
            actual_date = self.date_to_be_formatted.resolve(context)
            return actual_date.strftime(self.format_string)
        except template.VariableDoesNotExist:
            return ''

This is the example from the docs. You must first mark the value as a variable using template.Variable. The argument for that is the argument that holds the variable name. In the example, that’s date_to_be_formatted. This is saved as an instance variable on the node so it’s available later in the render method.

Then, in the render method, you attempt to resolve the Variable from the context (render has access to the context, which is why it’s done here). This is done by calling resolve on the instance variable you created in the __init__ method and passing it the context as it’s argument. The variable could potentially fail to resolve, which is why it needs to be in a try...except block.