Question

I have written a custom template tag which returns a number of users in the chat.

{% chat_online chat_channel %}

However, token seems to receive the value as chat_channel instead of the value of that variable.

What’s the matter?

Answer 1

Remember that template tags definitions ({% ... %})in your HTML are just pieces text being parsed by django’s template engine, so you need to tell django to actually lookup the variable in the context being rendered with the name chat_channel. This example from the docs is quite clear:

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

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

where template.Variable(date_to_be_formatted) is creating a template variable from the raw value passed to the template tag (blog_entry.date_updated in the example) and self.date_to_be_formatted.resolve(context) is finding the actual value of that variable in the template by resolving it against the context.