CODEWITHSUNDEEP
djangoobjectorminstance
Gustavo Reyes
Gustavo Reyes

Reputation: 1344

Django instanced object afected by update

def get_notifications(request):
    comments_send = EventUser.objects.filter(receive_id=request.user).order_by('-date')[:5]
    comments = EventUser.objects.filter(receive_id=request.user,read=False).order_by('-date')
    comments.update(read=True)
    return render(request, 'home/notifications.html', locals())

After creating an instance of EventUser, I am updating the object. After that I render the instanced object but it shows updated.

{% for c in comments_send %}
    ...
{% endfor %}

Why does this happen? How can I avoid it?

Upvotes: 0

Views: 26

Answers (2)

patsweet
patsweet

Reputation: 1558

This is happening because QuerySets are lazy.

So, although it appears that you are pulling out the comments_send before updated all comments with comments.update(read=True), the actual query being sent to the database may differ.

You can force evaluation of the queryset by converting it to a list:

comments_send = list(EventUser.objects.filter(receive_id=request.user).order_by('-date')[:5])

Upvotes: 1

stormlifter
stormlifter

Reputation: 3841

This is because the query is not executed until it is needed (django queryset is lazy by default) and by that time it has already been updated.

So you need to force the "comments_send" to be evaluated. You can force it to evaluate before by casting it to a list.

comments_send = list(comments_send)

before the

comments.update(read=True)

You can see when QuerySets are evaluated in the Django Documenation

Upvotes: 1

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