How should I solve this weird Primary Key error in Django?

Question

I have a Django to-do list app. In this app there is a page that gives all the details about a task like subtasks and notes, etc. The url of this page is like this "/todo/name of task". I wish to pass the pk of the task as well for security reasons. Also, if I check for a task in the database with its pk along with the title then this would allow a user to have multiple tasks with the same name. But as soon as I pass the pk with the URL, I face weird issues with subtasks and notes. This is my view function that handles the page of the task:

def todo_detail(request, title):
    try:
        todo = ToDo.objects.get(title=title, creator=request.user)
    except:
        return render(request, "ToDo/restrict_access.html")

    subtasks = SubTask.objects.filter(parent_task=todo)

    try:
        note = Notes.objects.get(parent_task=todo)
    except:
        note = Notes()

    if request.method == "POST":
        note_form = ToDoNotesForm(request.POST)
        subtask_form = SubTaskForm(request.POST)
        due_form = DueDateForm(request.POST)

        if note_form.is_valid():
            task_notes = note_form.cleaned_data.get("task_notes")

            new_note = Notes(content=task_notes)
            new_note.parent_task = todo
            new_note.save()

            todo.has_notes = True
            todo.save()

            messages.success(request, "Your notes are saved")

            return HttpResponseRedirect(request.META.get('HTTP_REFERER', '/'))

        elif subtask_form.is_valid():
            subtask_title = subtask_form.cleaned_data.get("sub_task")

            subtask = SubTask(title=subtask_title)
            subtask.parent_task = todo

            subtask.parent_task.num_of_subtasks += 1
            subtask.parent_task.save()

            subtask.save()

            messages.success(request, "Subtask added")

            return HttpResponseRedirect(request.META.get('HTTP_REFERER', '/'))

        elif due_form.is_valid():
            days = due_form.cleaned_data.get("due_date").lower()

            if days == "today":
                days = 0
            elif days == "tomorrow":
                days = 1
            elif days == "next week":
                days = 7
            elif days == "yesterday":
                days = -1
            elif days == "last week":
                days = -7
            else:
                days = int(days)

            today = datetime.datetime.today()
            due_date = today + datetime.timedelta(days=days)

            todo.due_date = due_date
            todo.save()

            messages.success(request, "Due Date added to task")

            return HttpResponseRedirect(request.META.get('HTTP_REFERER', '/'))

    else:
        note_form = ToDoNotesForm()
        subtask_form = SubTaskForm()
        due_form = DueDateForm()

    context = {
        "todo": todo,
        "note_form": note_form,
        "note": note,
        "subtask_form": subtask_form,
        "subtasks": subtasks,
        "due_form": due_form,
        "title": todo.title,
        "percentage": percentage
    }

    return render(request, "ToDo/detailed_view.html", context=context)

In the detail page, there are links to check, uncheck or edit a subtask or edit the notes. In the html page I have made sure to pass only the according pk to the editing or checking view fuctions.

There were some HTML code here that is not relevent

    {% if subtasks %}
        


        Subtasks for this task:
        

        
            {% for subtask in subtasks %}
                
                    {% if not subtask.done %}
                        {% if request.user_agent.is_mobile %}
                            
                                 {{ subtask.title }} 
                                

                                
                                 
                            
                        {% else %}
                            
                                 {{ subtask.title }}  
                                 
                                 
                            
                        {% endif %}
                    {% else %}
                        {% if request.user_agent.is_mobile %}
                            
                                 {{ subtask.title }} 
                                

                                 
                                 
                            
                        {% else %}
                             {{ subtask.title }}    
                        {% endif %}
                    {% endif %}
                
            {% endfor %}
            {% if percentage != 0 %}
                Your progress:
                 {{ percentage }}%
            {% endif %}
        
    {% endif %}

    {% if todo.has_notes %}
        

        Notes for this task:
        
            

            {{ note.content|linebreaks }}
            
            
        
        
            

            Notes added on: {{ note.date_added|date:"F d, Y" }}
            


            {% if note.date_edited != note.date_added %}
                Notes edited on: {{ note.date_edited|date:"F d, Y" }}
            {% endif %}
        

    {% else %}

        

        
            {% csrf_token %}
            
                Add notes
                {{ note_form|crispy }}
                
            
            
                
            
        

    {% endif %}


{% endblock content %}

As long as I am only passing the title to the detail page, all the other links work. But if I pass the pk of the task to the detail page, and I want to check a particular subtask, then this happens:

As you can see the pk after toggle-subtask is the pk for that subtask, yet Django is telling that it cannot find a ToDo object? To check the subtask there is a different URL and has no connection with the detail page. This doesn't make sense.

Any help on this issue will be seriously and hugely appreciated. Thank you all.

Edit: This is my view function that checks and unchecks a subtask:

@login_required
def toggle_subtask(request, pk):
    try:
        subtask = SubTask.objects.get(pk=pk)
        # Security check
        if subtask.parent_task.creator != request.user:
            return render(request, "ToDo/restrict_access.html")
    except:
        return render(request, "ToDo/restrict_access.html")



    if subtask.done:
        subtask.done = False
        subtask.save()

        messages.info(request, "Okay, take your time!")

    else:

        subtask.done = True
        subtask.save()

        messages.info(request, "Awesome!")

    return HttpResponseRedirect(request.META.get('HTTP_REFERER', '/'))

So apparently, I should've gotten error in the first place when visiting the details page if no ToDo was found. But I was able to get to the details page. The issue is when I want to check a subtask, they say that the ToDo is not found, but in reality I am checking for SubTask not ToDo.

damon · Accepted Answer

Your view function toggle_subtask isn't being routed to because todo_detail is getting routed to first.

From the django docs in How Django processes a request:

Django runs through each URL pattern in order, and stops at the first one that matches the requested URL, matching against path_info.

In your urls.py file, you can structure the urls so that the most specific ones (like /todo/toggle_subtask//) come before the least specific ones (like /todo//</code>):</p> <pre class="lang-py prettyprint-override"><code>from django.urls import path from . import views # Wherever your `views.py` should be imported from urlpatterns = [ # /todo/toggle_subtask/<pk>/ path('/todo/toggle_subtask/<int:pk>/', views.toggle_subtask), # /todo/<title>/ path('/todo/<str:title>/', views.todo_detail), ] </code></pre>

How should I solve this weird Primary Key error in Django?

Answers (2)

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