django.db.utils.IntegrityError：唯一约束失败：mode_setting.user_id

Question

I am new to Javascript, I am currently learning to debug errors that I am receiving in the Console.

In my project, I am adding a theme choosing option for each user logged into the website. Currently, it is showing the 2 themes when I click the buttons but it is not saving the theme for each user.

I have created an app in my Django Project and everything is as covered in the tutorial I am following except that in the console I am receiving errors every time I select a theme from the buttons:

(index):573 POST http://127.0.0.1:8000/update_theme/ 500 (Internal Server Error)

and in the Terminal this error:

django.db.utils.IntegrityError: UNIQUE constraint failed: mode_setting.user_id

Here is the base template:

    <link id="mystylesheet" href="{% static 'css/app-light.css' %}" type="text/css" rel="stylesheet">
        <!-- Mode -->
        <div id="mode" class="section" style="padding-top: 1rem; padding-bottom: 3rem;text-align: right">
            <button onclick="swapStyles('app-light.css')" type="button" class="btn btn-secondary">Light Mode</button>
            <button onclick="swapStyles('app-dark.css')" type="button" class="btn btn-dark">Dark Mode</button>
        </div>
        <!-- Mode -->

Javascript

    <script type="text/javascript">

        function getCookie(name) {
            var cookieValue = null;
            if (document.cookie && document.cookie !== '') {
                var cookies = document.cookie.split(';');
                for (var i = 0; i < cookies.length; i++) {
                    var cookie = cookies[i].trim();
                    // Does this cookie string begin with the name we want?
                    if (cookie.substring(0, name.length + 1) === (name + '=')) {
                        cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
                        break;
                    }
                }
            }
            return cookieValue;
        }
        var csrftoken = getCookie('csrftoken');

        var cssFile = "{% static 'css' %}"
        function swapStyles(sheet){
            document.getElementById('mystylesheet').href = cssFile + '/' + sheet
            localStorage.setItem('theme', sheet)

            updateTheme(sheet)
        }
        function loadSettings(){
            //Call data and set local storage

            var url = "{% url 'mode:user_settings' %}"
            fetch(url, {
                method:'GET',
                headers:{
                    'Content-type':'application/json'
                }
            })
            .then((response) => response.json())
            .then(function(data){

                console.log('Data:', data)

                var theme = data.value;

                if (theme == 'light.css' || null){
                    swapStyles('light.css')
                }else if(theme == 'dark.css'){
                    swapStyles('dark.css')
                }
            })
        }
        loadSettings()
        function updateTheme(theme){
            var url = "{% url 'mode:update_theme' %}"
            fetch(url, {
                method:'POST',
                headers:{
                    'Content-type':'application/json',
                    'X-CSRFToken':csrftoken,
                },
                body:JSON.stringify({'theme':theme})
            })
        }
    </script>

Here is the model

class Setting(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, related_name="mode",null=True,blank=True)
    name = models.CharField(max_length=200, null=True)
    value = models.CharField(max_length=200)

    def __str__(self):
        return self.name

Here is the views.py

def userSettings(request):
    user = request.user
    setting = getattr(user, 'setting', None)

    if setting:
        seralizer = UserSerailizer(setting, many=False)
        return JsonResponse(seralizer.data, safe=False)
    else:
        return JsonResponse({'message': "User don't have a setting."}, safe=False)


def updateTheme(request):
    data = json.loads(request.body)
    theme = data['theme']

    user=request.user
    setting = Setting.objects.get_or_create(user=user, value=theme, name=user.username)
    setting.save()
    print('Request:', theme)
    return JsonResponse('Updated..', safe=False)

urls.py

app_name = 'mode'


urlpatterns = [
    path('user_settings/', views.userSettings, name="user_settings"),
    path('update_theme/', views.updateTheme, name="update_theme"),
]

serializer.py

from .models import *

class UserSerailizer(serializers.ModelSerializer):
    class Meta:
        model = Setting
        fields = '__all__'

My question reason I am receiving this error and how to fix it?

Answer 1

You are using get_or_create wrong as you are filtering by all fields and not finding already existing instance in database which results in get_or_create trying to create another one

So you should move fields that just need to be updated to defaults as documented

setting = Setting.objects.get_or_create(user=user, defaults={'value': theme, 'name'= user.username)

---

Additionally

• storing user.username as field is data duplication which makes no sense
• calling setting.save() after get_or_create is unnecessary as you can use update_or_create instead