update fields before saving

Using Django Forms & APIs
1

I am getting familiar with Django more and more. I am building a planning app. Shifts, sites, users are the main ingredients. I really am excited how versatile Django is and most of all how robust everything works. Straigth forward things are going very smooth. But I want to add some intelligence to make live easier. I post here a form template together with the form logic. I have in my Shift model 2 fields ‘user’ and ‘ex_user’.

user = models.ForeignKey(User, blank=True, null=True, on_delete=models.CASCADE)
ex_user = models.ForeignKey(User, blank=True, null=True, on_delete=models.CASCADE, related_name='exuser')

When I edit a shift I want 2 things:

  1. Only when user is changed, copy initial user to ex_user when saving the record.
  2. When user is not changed do nothing.

Copy user to ex_user when user changed works fine. Only when user is not changed, ex_user is cleaned to null. I just can’t find why and how this is happening. Would be very thankful if somebody can take a look and advise me how to solve this.
The main problem I want to solve is keep the ex_user value when user is not changed

Thanks for your concern!

#My ShiftForm:

class ShiftForm(forms.ModelForm):
    class Meta:
        model = Shift
        fields = '__all__'  # 'ex_user' is not included explicitly

    def __init__(self, *args, **kwargs):
        super(ShiftForm, self).__init__(*args, **kwargs)
        # Store the initial user if the instance already exists
        if self.instance and self.instance.pk:
            self._initial_user = getattr(self.instance, 'user', None)

    def save(self, commit=True):
        if self.instance.pk:
            # Get the initial user
            initial_user = getattr(self, '_initial_user', None)

            # Get the current user from the cleaned data
            current_user = self.cleaned_data.get('user')

            # Update ex_user only if the user has been changed
            if initial_user is not None and current_user != initial_user:
                self.instance.ex_user = initial_user
            elif 'ex_user' not in self.changed_data:
                # If ex_user was not part of the changed fields, retain its original value
                self.instance.ex_user = getattr(self.instance, 'ex_user', None)

            if self.instance.invoiced and not self.instance.copied:
                # Logic for handling invoiced and not copied instances
                new_shift = Shift(**self.cleaned_data)
                new_shift.shift_title += " NEW"
                new_shift.source = self.instance.pk
                new_shift.invoiced = None
                new_shift.id = None

                if commit:
                    new_shift.save()
                    self.instance.copied = self.instance.id
                    self.instance.save(update_fields=['copied'])

                return new_shift

            elif self.instance.invoiced and self.instance.copied:
                raise ValueError("This record is locked and cannot be edited or copied.")

        return super(ShiftForm, self).save(commit=commit)

And here my template:

# edit_shift.html:

{% extends 'base.html' %}

{% load custom_filters %}

{% load static %}

{% block additional_css %}
    <link rel="stylesheet" type="text/css" href="{% static 'css/form.css' %}">
{% endblock %}

{% block content %}

    <div class="edit-shift-page">

        <form class="form bg" method="post">

            <div class="form-buttons">

                <div class="edit-id">Id: {{ shift.id }}</div>

                <div class="button-container">

                    <a href="{% url 'new_shift' %}" class="btn btn-sm icon-color"><i
                            class="fa-solid fa-circle-plus fa-2xl"></i></a>
                    <button type="submit" class="btn btn-primary btn-sm custom-button" id="saveButton">Save</button>
                    <button type="button" class="btn btn-primary btn-sm custom-button"
                            onclick="location.href='{% url 'home' %}'">Cancel
                    </button>

                </div>
            </div>

            {% csrf_token %}

            <div class="form-group">
                <label for="{{ form.status.id_for_label }}">{{ form.status.label }}</label>
                <select class="form-select round small-size select-value form-small"
                        id="{{ form.status.id_for_label }}"
                        name="{{ form.status.html_name }}">
                    {% for choice in form.status.field.choices %}
                        <option value="{{ choice.0 }}"
                                {% if choice.0 == form.status.value %}selected{% endif %}>
                            {{ choice.1 }}
                        </option>
                    {% endfor %}
                </select>
            </div>

            <div class="form-group">
                <label for="{{ form.shift_title.id_for_label }}">{{ form.shift_title.label }}</label>
                <input type="text" class="form-control round form-control-sm shift-title" id="shift_title"
                       name="shift_title"
                       value="{{ shift.shift_title }}">
            </div>

            <div class="form-group">
                <label for="{{ form.job.id_for_label }}">{{ form.job.label }}</label>
                <select class="form-select round form-small small-size select-value" id="job" name="job">
                    {% for choice in form.job.field.choices %}
                        <option value="{{ choice.0 }}"
                                {% if choice.0 == shift.job.id %}selected{% endif %}>{{ choice.1 }}</option>
                    {% endfor %}
                </select>
            </div>

            <div class="form-group">
                <label for="{{ form.start_date.id_for_label }}">{{ form.start_date.label }}</label>
                <input type="date" class="form-control round form-control-sm small-size" id="start_date"
                       name="start_date"
                       value="{{ shift.start_date|date:'Y-m-d' }}">
            </div>

            <div class="form-group">
                <label for="{{ form.start_time.id_for_label }}">{{ form.start_time.label }}</label>
                <input type="time" class="form-control round form-control-sm small-size" id="start_time"
                       name="start_time"
                       value="{{ shift.start_time }}">
            </div>

            <div class="form-group">
                <label for="{{ form.end_time.id_for_label }}">{{ form.end_time.label }}</label>
                <input type="time" class="form-control round form-control-sm small-size" id="end_time" name="end_time"
                       value="{{ shift.end_time }}">
            </div>

            <div class="samen round">
                <div class="form-group">
                    <label for="{{ form.site.id_for_label }}">{{ form.site.label }}</label>
                    <select class="form-select round select-value form-select-sm select2-enable"
                            id="{{ form.site.id_for_label }}"
                            name="{{ form.site.name }}"
                            data-placeholder="Selecteer locatie">
                        <option value="" {% if not form.site.value %}selected{% endif %}>Select an option</option>
                        {% for site in sites %}
                            <option value="{{ site.id }}"
                                    {% if form.site.value == site.id %}selected{% endif %}>{{ site }}</option>
                        {% endfor %}
                    </select>
                </div>

                <div class="contactdetails">
                    <b>Tel:</b> <span id="siteDetails.phone">{{ shift.site.phone }}</span>
                </div>
            </div>


            <div class="samen round">
                <div class="form-group">
                    <label for="{{ form.user.id_for_label }}">{{ form.user.label }}</label>
                    <select class="form-select round select-value form-select-sm select2-enable"
                            id="{{ form.user.id_for_label }}"
                            name="{{ form.user.name }}"
                            data-placeholder="Selecteer zorgverlener">
                        <option value="" {% if not form.user.value %}selected{% endif %}>Select an option</option>
                        {% for user in users %}
                            <option value="{{ user.id }}"
                                    {% if form.user.value == user.id %}selected{% endif %}>{{ user.user_profile }}</option>
                        {% endfor %}
                    </select>
                </div>

                <div class="contactdetails">
                    {% if shift.user %}
                        <b>Email:</b>
                        <a href="mailto:{{ shift.user.email }}" id="userDetails.email">{{ shift.user.email }}</a>
                    {% else %}
                        <b>Email:</b> <a href="#" id="userDetails.email"></a>
                    {% endif %}
                    /
                    <b>Tel:</b> <span id="userDetails.phone">{% if shift.user %}
                    {{ shift.user.user_profile.phone }}{% endif %}</span>
                </div>

                <div class="ex-user"><b>ex_user: </b>{{ form.instance.ex_user_profile|default_if_none:"No ex user selected." }}</div>


            </div>


            <div class="form-group">
                <label for="{{ form.user_notes.id_for_label }}">{{ form.user_notes.label }}</label>
                <textarea class="form-control form-control-sm round" id="user_notes"
                          name="user_notes">{{ shift.user_notes }}</textarea>
            </div>

            <div class="form-group">
                <label for="{{ form.customer_notes.id_for_label }}">{{ form.customer_notes.label }}</label>
                <textarea class="form-control form-control-sm round" id="customer_notes"
                          name="customer_notes">{{ shift.customer_notes }}</textarea>
            </div>

            <div class="form-group">
                <label for="{{ form.admin_notes.id_for_label }}">{{ form.admin_notes.label }}</label>
                <textarea class="form-control form-control-sm round" id="admin_notes"
                          name="admin_notes">{{ shift.admin_notes }}</textarea>
            </div>

            <div class="form-group">
                <!-- Hidden input for 'invoiced' -->
                <input type="hidden" id="invoiced" name="invoiced" value="{{ shift.invoiced|default_if_none:'' }}">
            </div>

            <div class="form-group">
                <!-- Hidden input for 'copied' -->
                <input type="hidden" id="copied" name="copied" value="{{ shift.copied|default_if_none:'' }}">
            </div>

            <div class="form-group">
                <!-- Hidden input for 'source' -->
                <input type="hidden" id="source" name="source" value="{{ shift.source|default_if_none:'' }}">
            </div>

            <div class="form-group">
                <!-- Hidden input for 'update' -->
                <input type="hidden" id="update" name="update" value="{{ shift.update|default_if_none:'' }}">
            </div>

            <!-- REFERAL ONLY INFO -->
            <div class="info-row">
                <div class="info-item">
                    <div>I: {{ form.invoiced.value|default_if_none:"" }}</div>
                </div>

                <div class="info-item">
                    <div>C: {{ form.copied.value|default_if_none:"" }}</div>
                </div>

                <div class="info-item">
                    <div>S: {{ form.source.value|default_if_none:"" }}</div>
                </div>

                <div class="info-item">
                    <div>U: {{ form.update.value|default_if_none:"" }}</div>
                </div>
            </div>

        </form>

        <script>
            $(document).ready(function () {
                $('.select2-enable').select2({
                    placeholder: "Select an option",
                    allowClear: true
                });
            });
        </script>

        <script>
            $(document).ready(function () {
                // Function to check the copied field and disable save
                function checkCopiedAndDisableSave() {
                    var copiedValue = $('#copied').val();
                    if (copiedValue !== '') {
                        $('#saveButton').prop('disabled', true);
                    } else {
                        $('#saveButton').prop('disabled', false);
                    }
                }

                // Check on page load
                checkCopiedAndDisableSave();

                // Check when form changes
                $('form').change(checkCopiedAndDisableSave);
            });
        </script>

    </div>

{% endblock %}

To be complete also my view:

#shift_edit view:

def shift_edit(request, pk=None):
    shift = None
    if pk:
        try:
            shift = Shift.objects.get(pk=pk)
        except Shift.DoesNotExist:
            return HttpResponseNotFound('Shift not found')

    # Fetching sites and users for context
    sites = Site.objects.select_related('customer').all()
    users = User.objects.select_related('user_profile__job').all()

    if request.method == 'POST':
        form = ShiftForm(request.POST, instance=shift)
        if form.is_valid():
            form.save()  # Save the form (update or create new shift)
            return redirect('home')  # Always redirect to 'home' after saving
    else:
        form = ShiftForm(instance=shift)

    context = {
        'form': form,
        'shift': shift,
        'sites': sites,
        'users': users,
    }

    return render(request, 'forms/edit_shift.html', context)
2

I’m not sure I understand the intent of your comment here.

You’re explicitly stating that all fields are part of the form.

Is ex_user a field in the Shift model? If so, then it is a field in the form - and if you don’t render that field, its value will be null.

If you don’t want the ex_user field in the form, then use the exclude attribute.

3

Hi Ken, As you can see ex_user is not a form field but is only displayed as a referal value in this way:

<div class="ex-user"><b>ex_user: </b>{{ form.instance.ex_user_profile|default_if_none:"No ex user selected." }}</div>

Should ex_user be a form field to prevent it from getting cleared?

4

Again:

Keep in mind that a Django Form is a Python class that is (usually) used to create an HTML form - which is not the same thing as a Django Form.

You want to properly identify the Model fields being used in your form definition.

5

Yes ex_user is part of my Shift model:

class Shift(models.Model):
    status = models.ForeignKey('Status', on_delete=models.CASCADE)
    shift_title = models.CharField('Shift title', max_length=255)
    job = models.ForeignKey('Jobs', blank=True, null=True, on_delete=models.CASCADE)
    start_date = models.DateField('Start date', db_index=True)
    start_time = models.TimeField('Start time', db_index=True)
    end_time = models.TimeField('End time')
    site = models.ForeignKey('Site', blank=True, null=True, on_delete=models.CASCADE)
    user = models.ForeignKey(User, blank=True, null=True, on_delete=models.CASCADE)
    ex_user = models.ForeignKey(User, blank=True, null=True, on_delete=models.CASCADE, related_name='exuser')
    user_notes = models.TextField(blank=True, null=True)
    customer_notes = models.TextField(blank=True, null=True)
    admin_notes = models.TextField(blank=True, null=True)
    invoiced = models.IntegerField(blank=True, null=True)
    copied = models.IntegerField(blank=True, null=True)
    source = models.IntegerField(blank=True, null=True)
    update = models.IntegerField(blank=True, null=True)
    history = HistoricalRecords()

    def __str__(self):
        return self.shift_title

    def ex_user_profile(self):
        # Retrieve the associated profile for ex_user
        if self.ex_user:
            return self.ex_user.user_profile
        else:
            return None
6

I added ex_user to the form like this:

<div class="form-group">
                    <label for="{{ form.ex_user.id_for_label }}">{{ form.ex_user.label }}</label>
                    <input type="text" class="form-control round form-control-sm shift-title" id="shift_ex_user"
                           name="shift_title"
                           value="{{ shift.ex_user_profile }}">
                </div>

But still ex_user is cleared even when user did not change.

This is what I want to see:

  1. If ‘user’ is changed, set ‘ex_user’ to ‘initial_user’.
  2. If ‘user’ is not changed, do not change ‘ex_user’.
7

Let me try rephrasing this.

Create your form specifying the fields that you want to use in the form.

Do not use fields='__all__'.

Identify the specific list of fields that you are using in the form. (Or, use the exclude attribute and list the fields that you are not using in the form.)

8

exclude = [ ‘ex_user’ ] did the job! Thanks Ken!