How to recognize the first loop call in if statement? - django

Question

I have code in template:
{% for p in products %}
{% if p.parent == None %}
<li class="{% if forloop.first %}active{% endif %}">
{{ p.name|upper }}
</li>
{% endif %}
{% endfor %}
In my case class "active" shows me in li with parent != None. I can't use [...]filter(parent=None) in view as I must have a complete list of products.
The problem is that if first object.parent in products =! None Django will think that the first iteration happened so that I will never add active to my class.
So I want to check when the first iteration with successful if statement happened. Any ways to do this?

Answer 1

You could recover the first element in the view in python, add it to the context and then test in your template :
{% for p in products %}
{% if not p.parent %}
<li class="{% if p == first_element %}active{% endif %}">
{{ p.name|upper }}
</li>
{% endif %}
{% endfor %}

Answer 2

{% with is_first=True %}
{% for p in products %}
{% if p.parent == None %}
<li class="{% if is_first %}active{% endwith % }{% endif %}">
{{ p.name|upper }}
</li>
{% endif %}
{% endfor %}
Can not test now - but perhaps that work!

Answer 3

You can put this on the objects themselves or as extra variable, when you build the context. Do code like this:
e.g. instead of:
ctx['products'] = Product.objects.all()
do something like this:
ctx['products'] = list(Product.objects.all())
is_first = True
for p in ctx['products']:
p.is_active = p.parent is None and is_first:
is_first = False
Then in the template, just do:
<li class="{% if p.is_active %}active{% endif %}">
{{ p.name|upper }}
</li>
If you don't want to write on the object, use extra variable
ctx['products'] = list(Product.objects.all())
is_first = True
for p in ctx['products']:
if p.parent is None and is_first:
ctx['active_id'] = p.id
break
Then in the template, just do:
<li class="{% if p.id == active_id %}active{% endif %}">
{{ p.name|upper }}
</li>

Answer 4

You can also use forloop.counter like this
{% for p in products %}
{% if forloop.counter == 0 %}
<li class="{% if is_first %}active{% endwith % }{% endif %}">
{{ p.name|upper }}
</li>
{% endif %}
{% endfor %}