Django 表单字段验证

Question

I have a form that requires a URL as input. I would like to check if the URL begins with http:// or https:// .

If it doesn't have one of these two 'stings' in the beginning, the form submission should give an error.

I don't have any clue on how to get started with this and could not find any info based on my limited knowledge of django and I have no clue what search terms to look up.

A basic hint would be a great help.

Thanks!

My current forms.py has a form based on a model:

class AddUrlForm(forms.ModelForm):

    class Meta:
        model = forwards
        # fields = '__all__'
        exclude = ["user", "counterA", "counterB", "shortcodeurl", "uniqueid"]

models.py:

class forwards(models.Model):
    uniqueid = models.AutoField(primary_key=True)
    user = models.CharField(max_length = 150)
    urlA = models.CharField(verbose_name="URL Version A", max_length = 254)
    counterA = models.DecimalField( max_digits=19, decimal_places=0,default=Decimal('0'))
    urlB = models.CharField(verbose_name="URL Version B",max_length = 254)
    counterB = models.DecimalField( max_digits=19, decimal_places=0,default=Decimal('0'))
    timestamp = models.DateTimeField('date created', auto_now_add=True)
    shortcodeurl = models.CharField(max_length = 254)

html segment where that shows how the form is integrated:

        <form method="post">
            {% csrf_token %}
            {% for field in forwardform %}
                <span>{{ field.label_tag }} </span>
                <p style="color: black">{{ field }} </p>
                {% for error in field.errors %}
                        <p style="color: red">{{ error }}</p>
                {% endfor %}
            {% endfor %}
        <button class="btn btn-outline btn-xl type="submit">Generate URL</button>
        </form>

views.py:

def forwardthis(request):
    forwardform = AddUrlForm(request.POST or None)
    if forwardform.is_valid():
        forward = forwardform.save(commit=False)
        forward.user = request.user.username
        forward = forwardform.save()
        uniqueid_local = forward.uniqueid
        uniqueid_local_bytes = uniqueid_local.to_bytes((uniqueid_local.bit_length() + 7) // 8, byteorder='little')
        shortcodeurl_local  = urlsafe_base64_encode(uniqueid_local_bytes)
        forward.shortcodeurl = shortcodeurl_local
        forward.save()
        return HttpResponseRedirect('/forwardthis')
    query_results = forwards.objects.filter(user=request.user.username)
    query_results_qty = query_results.count()
    click_results = clickstats.objects.filter(user=request.user.username)
    template = loader.get_template('forwardthis.html')
    context = {
        'forwardform': forwardform ,
        'query_results':query_results,
        'query_results_qty': query_results_qty
    }
    return HttpResponse(template.render(context,request))

Answer 1

You can create a validation method for each form field. def clean_FIELDNAME() . I supose the url field is shortcodeurl :

class AddUrlForm(forms.ModelForm):

    def clean_shortcodeurl(self):
        cleaned_data = self.clean()
        url = cleaned_data.get('shortcodeurl')
        if not is_valid_url(url):  # You create this function
            self.add_error('shortcodeurl', "The url is not valid")
        return url

    class Meta:
        model = forwards
        # fields = '__all__'
        exclude = ["user", "counterA", "counterB", "shortcodeurl", "uniqueid"]

Answer 2

For anyone coming here in 2021.

Nowadays Django provides the tools to achieve this kind of validation.

Based on Django 3.2 documentation

from django import forms
from django.core.exceptions import ValidationError

class AddUrlForm(forms.ModelForm):

    class Meta:
        model = forwards
        # fields = '__all__'
        exclude = ["user", "counterA", "counterB", "shortcodeurl", "uniqueid"]

    def clean_shortcodeurl(self):
        data = self.cleaned_data['shortcodeurl']
        if "my_custom_example_url" not in data:
            raise ValidationError("my_custom_example_url has to be in the provided data.")
        return data