How Do I Pass the Primary Key to a Django UpdateView?

I’m building an UpdateIngredientView to update a restaurant's ingredient quantity and price_per_unit fields, but I’m encountering an error asking for a primary key or slug. I followed Django For Beginners and added a URL tag in my template like this:

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<!-- start new HTML... -->
<a href="{% url 'post_edit' post.pk %}">+ Edit Blog Post</a> <!-- end new HTML... -->
{% endblock content %}

My UpdateIngredientView in views.py is defined as:

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class UpdateIngredientView(UpdateView):  # I am thinking this is an UpdateView
    model = Ingredient
    template_name = 'inventory/form_template.html'
    fields = ["quantity", "price_per_unit"]
    success_url = reverse_lazy('ingredientupdate')

In models.py, the Ingredient model defines a get_absolute_url method using the object's pk:

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def get_absolute_url(self):
    return reverse("updateingredient", kwargs={"pk": self.pk})

However, when I click the link, I receive the following error:

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Traceback (most recent call last):
  File "/.../django/views/generic/detail.py", line 46, in get_object
    raise AttributeError(
AttributeError: Generic detail view UpdateIngredientView must be called with either an object pk or a slug in the URLconf.

How should I supply the pk value in my URLconf or view so that UpdateView can correctly identify the Ingredient instance I want to update? Any guidance would be appreciated.