CODEWITHSUNDEEP
djangodjango-templates
wei
wei

Reputation: 3482

How django's template tag "include" work with None

I'm using an include tag in my templates like this:

{% include fragment_variable %}

where fragment_variable is a context variable that might not exist. I wonder if it will blow up when fragment_variable is not in context variables or is None.

NOTE: actually I tested this code in two different environments (both using Django 1.7) and got two different results (one blew up with some stack trace for templates lookups and the other just failed silently). So I'm curious if there's a setting in django that controls how template rendering behaves when "include" tag can't find a valid template.

Upvotes: 0

Views: 263

Answers (1)

Shang Wang
Shang Wang

Reputation: 25549

{% if fragment_variable %}
    {% include fragment_variable %}
{% else %}
    <!-- something else -->
{% endif %}

Edit:

Since you are using django version prior to 1.8, take a look at the setting TEMPLATE_STRING_IF_INVALID, it sets the default value for invalid variables.

Also take a look at How invalid variables are handled:

Generally, if a variable doesn’t exist, the template system inserts the value of the engine’s string_if_invalid configuration option, which is set to '' (the empty string) by default.

This behavior is slightly different for the if, for and regroup template tags. If an invalid variable is provided to one of these template tags, the variable will be interpreted as None. Filters are always applied to invalid variables within these template tags.

For that matter, I still consider using if is the best exercise.

Upvotes: 1

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