Question

I’ve created a custom template tag and want to have a helper method in my template.Node but when I call the helper method I get the error,

global name 'prepend_to_some_str' is not defined

Here’s the code that causes the error.

from django import template
from django.template.loader import render_to_string
from easy_maps.models import Address
register = template.Library()

@register.tag
def foo(parser, token):
    params = token.split_contents()
    return FooNode(params[1])

class FooNode(template.Node):
    def __init__(self, some_str):
        self.some_str = template.Variable(some_str)

    def prepend_to_some_str(some_str):
        return "foo" + some_str

    def render(self, context):
        try:
            some_str = self.some_str.resolve(context)

            context.update({
                'full_str': prepend_to_some_str(some_str),
            })
            return render_to_string('foo.html', context_instance=context)
        except template.VariableDoesNotExist:
            return ''

Of course if I move the helper method prepend_to_some_str to the global scope it works just fine as in the code below.

from django import template
from django.template.loader import render_to_string
from easy_maps.models import Address
register = template.Library()

@register.tag
def foo(parser, token):
    params = token.split_contents()
    return FooNode(params[1])

def prepend_to_some_str(some_str):
    return "foo" + some_str

class FooNode(template.Node):
    def __init__(self, some_str):
        self.some_str = template.Variable(some_str)

    def render(self, context):
        try:
            some_str = self.some_str.resolve(context)

            context.update({
                'full_str': prepend_to_some_str(some_str),
            })
            return render_to_string('foo.html', context_instance=context)
        except template.VariableDoesNotExist:
            return ''

Does anyone know why FooNode is looking for prepend_to_some_str in the global scope instead of the class scope in the code that causes the error?

Thanks.

Answer 1

You should define it with self as a first argument and call like: self.prepend_to_some_str(some_str)