How do I pass foreign key values to Django forms for creating related Problem and Solution entries?

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Hello,

I have an overview page showing responsibilities, and by clicking on a responsibility, I navigate to the view responsibility_details which displays detailed information (bottleneck parts, drawings, meeting data, etc.). My models allow a Problem to depend on a Responsibility and a Solution to depend on a Problem. I want to create forms for adding a Problem or a Solution, but I need to pass the appropriate foreign key (responsibility_id for Problem creation and problem_id for Solution creation).

For example, my view is defined as follows:

PYTHON
def responsibility_details(request, id):
    responsibility = get_object_or_404(Responsibility, id=id)

    bottleneck_parts = BottleneckPart.objects.filter(cost_bearer=responsibility.project.cost_bearer).filter(department=responsibility.team.department.name).filter(system=responsibility.system.number)
    
    drawings = Drawing.objects.filter(cost_bearer=responsibility.project.cost_bearer).filter(department=responsibility.team.department.name).filter(system=responsibility.system.number).order_by('drawing_number').values()
    drawings_filter = DrawingFilter(request.GET, queryset=drawings)
    drawings = drawings_filter.qs

    drawings_visibility = Drawing.objects.filter(cost_bearer=responsibility.project.cost_bearer).filter(department=responsibility.team.department.name).filter(system=responsibility.system.number).order_by('drawing_number').values()

    project_rounds = Meeting.objects.filter(cost_bearer=responsibility.project.cost_bearer).filter(system=responsibility.system.number).filter(title='Projektrunde').order_by('description', 'subject', 'item', 'date', 'responsibility').values()

    working_meetings = Meeting.objects.filter(cost_bearer=responsibility.project.cost_bearer).filter(system=responsibility.system.number).filter(title='Working Meeting').order_by('description', 'subject', 'item', 'date', 'responsibility').values()

    context = {'responsibility': responsibility, 'bottleneck_parts': bottleneck_parts, 'drawings': drawings, 'project_rounds': project_rounds, 'working_meetings': working_meetings, 'drawings_filter': drawings_filter, 'drawings_visibility': drawings_visibility}

    return render(request, 'systemcockpit/responsibility_details.html', context)

The urls.py is as follows:

PYTHON
urlpatterns = [
    path('', views.responsibilities_overview, name='responsibilities-overview'),
    path('responsibility-details/<int:id>/', views.responsibility_details, name='responsibility-details'),
]

Suppose my ProblemForm looks like this:

PYTHON
from django import forms

class ProblemForm(forms.Form):
    # responsibility_id - how do i get it?
    summary = forms.CharField()
    description = forms.CharField()
    # user - should be automatically filled with the logged in user

And my models are defined as follows:

PYTHON
class Problem(models.Model):
    responsibility = models.ForeignKey(Responsibility, on_delete=models.CASCADE, verbose_name='Verantwortlichkeit', related_name='problems')
    summary = models.CharField(max_length=150, verbose_name='Zusammenfassung')
    description = models.TextField(verbose_name='Beschreibung')
    created_at = models.DateTimeField(auto_now_add=True, editable=False, blank=True, verbose_name='Erstelldatum')
    updated_at = models.DateTimeField(auto_now=True, editable=False, blank=True, verbose_name='Änderungsdatum')
    user = models.ForeignKey('auth.User', on_delete=models.SET_DEFAULT, default=1, editable=False, verbose_name='Ersteller / Änderer')

    class Meta:
        verbose_name = 'Problem'
        verbose_name_plural = 'Probleme'

    def __str__(self):
        return f'{self.responsibility} | {self.summary}'
    
class Solution(models.Model):
    problem = models.OneToOneField(Problem, on_delete=models.CASCADE, verbose_name='Problem', related_name='solutions')
    summary = models.CharField(max_length=150, verbose_name='Zusammenfassung')
    description = models.TextField(verbose_name='Beschreibung')
    created_at = models.DateTimeField(auto_now_add=True, editable=False, blank=True, verbose_name='Erstelldatum')
    updated_at = models.DateTimeField(auto_now=True, editable=False, blank=True, verbose_name='Änderungsdatum')
    user = models.ForeignKey('auth.User', on_delete=models.SET_DEFAULT, default=1, editable=False, verbose_name='Ersteller / Änderer')

    class Meta:
        verbose_name = 'Maßnahme'
        verbose_name_plural = 'Maßnahmen'

    def __str__(self):
        return f'{self.problem} | {self.summary}'

My question is: Do I have to handle passing the foreign key (responsibility_id or problem_id) within the responsibility_details view, or is there a cleaner method to accomplish this? I would appreciate a small code snippet or explanation of the alternative approach.

Best regards,
Patrick

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Answers 1

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1 Answer

Answer by StackOverflow TychoAI Agent • 9 days ago

Handling Foreign Keys in Django Forms

For your scenario with related models (Responsibility → Problem → Solution), there are a few clean approaches to handle the foreign key relationships in your forms. I'll outline the best approach using Django's ModelForm, which is more appropriate than a regular Form in this case.

Using ModelForm with Hidden Fields

Instead of using a regular Form, you should use ModelForm which is designed to work with models:

PYTHON
from django import forms
from .models import Problem, Solution

class ProblemModelForm(forms.ModelForm):
    class Meta:
        model = Problem
        fields = ['summary', 'description']
        # Exclude responsibility and user as they'll be set in the view

class SolutionModelForm(forms.ModelForm):
    class Meta:
        model = Solution
        fields = ['summary', 'description']
        # Exclude problem and user as they'll be set in the view

Then modify your view to handle both displaying the responsibility details and processing the form:

PYTHON
def responsibility_details(request, id):
    responsibility = get_object_or_404(Responsibility, id=id)
    
    # Handle Problem form submission
    if request.method == 'POST' and 'submit_problem' in request.POST:
        problem_form = ProblemModelForm(request.POST)
        if problem_form.is_valid():
            problem = problem_form.save(commit=False)
            problem.responsibility = responsibility
            problem.user = request.user
            problem.save()
            return redirect('responsibility-details', id=id)
    else:
        problem_form = ProblemModelForm()
    
    # Your existing code for fetching related data
    bottleneck_parts = BottleneckPart.objects.filter(cost_bearer=responsibility.project.cost_bearer)
    # ... other queries ...
    
    context = {
        'responsibility': responsibility,
        'bottleneck_parts': bottleneck_parts,
        'drawings': drawings,
        'project_rounds': project_rounds,
        'working_meetings': working_meetings,
        'drawings_filter': drawings_filter,
        'drawings_visibility': drawings_visibility,
        'problem_form': problem_form,
    }
    
    return render(request, 'systemcockpit/responsibility_details.html', context)

For Solution Creation

You would need a separate view for creating a solution for a specific problem:

PYTHON
def create_solution(request, problem_id):
    problem = get_object_or_404(Problem, id=problem_id)
    
    if request.method == 'POST':
        solution_form = SolutionModelForm(request.POST)
        if solution_form.is_valid():
            solution = solution_form.save(commit=False)
            solution.problem = problem
            solution.user = request.user
            solution.save()
            return redirect('responsibility-details', id=problem.responsibility.id)
    else:
        solution_form = SolutionModelForm()
    
    context = {
        'problem': problem,
        'solution_form': solution_form,
    }
    
    return render(request, 'systemcockpit/create_solution.html', context)

Add this to your URLs:

PYTHON
urlpatterns = [
    # Existing paths
    path('responsibility-details/<int:id>/', views.responsibility_details, name='responsibility-details'),
    path('create-solution/<int:problem_id>/', views.create_solution, name='create-solution'),
]

Template Example

In your responsibility_details.html template:

HTML
<!-- Display responsibility details -->
<h1>{{ responsibility.title }}</h1>
<!-- Other details -->

<!-- Problem creation form -->
<h2>Add a Problem</h2>
<form method="post">
    {% csrf_token %}
    {{ problem_form.as_p }}
    <button type="submit" name="submit_problem">Save Problem</button>
</form>

<!-- List existing problems -->
<h2>Problems</h2>
{% for problem in responsibility.problems.all %}
    <div>
        <h3>{{ problem.summary }}</h3>
        <p>{{ problem.description }}</p>
        <a href="{% url 'create-solution' problem_id=problem.id %}">Add Solution</a>
    </div>
{% endfor %}

This approach:

Uses ModelForm to handle model validation
Sets the foreign key in the view rather than the form
Uses the commit=False pattern to modify the object before saving
Separates concerns by having different views for different actions

This is cleaner than trying to handle everything in a single view and keeps your code more maintainable.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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