Built-in Form Field Validations in Django Forms are the default validations that come predefined to all fields. Every field comes in with some built-in validations from Django validators. Each Field class constructor takes some fixed arguments.
The error_messages argument lets you specify manual error messages for attributes of the field. The error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override. For example, here is the default error message:
>>> from django import forms
>>> generic = forms.CharField()
>>> generic.clean('')
Traceback (most recent call last):
...
ValidationError: ['This field is required.']
And here is a custom error message:
>>> name = forms.CharField(
error_messages={
'required': 'Please enter your name'
})
>>> name.clean('')
Traceback (most recent call last):
...
ValidationError: ['Please enter your name']
Syntax
field_name = models.Field(option = value)
Django Form Field Validation error_messages Explanation
Illustration of error_messages using an Example. Consider a project named neveropen having an app named Lazyroar.
Refer to the following articles to check how to create a project and an app in Django.
Enter the following code into forms.py file of Lazyroar app. We will be using CharField for experimenting for all field options.
from django import forms class GeeksForm(forms.Form): Lazyroar_field = forms.CharField( error_messages = { 'required':"Please Enter your Name" }) |
Add the Lazyroar app to INSTALLED_APPS
# Application definition INSTALLED_APPS = [ 'django.contrib.admin', 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.messages', 'django.contrib.staticfiles', 'Lazyroar',] |
Now to render this form into a view we need a view and a URL mapped to that view. Let’s create a view first in views.py of Lazyroar app,
from django.shortcuts import renderfrom .forms import GeeksForm # Create your views here.def home_view(request): context = {} form = GeeksForm(request.POST or None) context['form'] = form if request.POST: if form.is_valid(): temp = form.cleaned_data.get("Lazyroar_field") print(temp) return render(request, "home.html", context) |
Here we are importing that particular form from forms.py and creating an object of it in the view so that it can be rendered in a template.
Now, to initiate a Django form you need to create home.html where one would be designing the stuff as they like. Let’s create a form in home.html.
<form method = "POST"> {% csrf_token %} {{ form }} <input type = "submit" value = "Submit"></form> |
Finally, a URL to map to this view in urls.py
from django.urls import path # importing views from views..pyfrom .views import home_view URLpatterns = [ path('', home_view ),] |
Let’s run the server and check what has actually happened, Run
Python manage.py runserver
Now let’s try to submit it empty and check if required error_message has been overridden.
Thus the field is displaying a custom error message for required attribute of Charfield.
More Built-in Form Validations
| Field Options | Description |
|---|---|
| required | By default, each Field class assumes the value is required, so to make it not required you need to set required=False |
| label | The label argument lets you specify the “human-friendly” label for this field. This is used when the Field is displayed in a Form. |
| label_suffix | The label_suffix argument lets you override the form’s label_suffix on a per-field basis. |
| widget | The widget argument lets you specify a Widget class to use when rendering this Field. See Widgets for more information. |
| help_text | The help_text argument lets you specify descriptive text for this Field. If you provide help_text, it will be displayed next to the Field when the Field is rendered by one of the convenience Form methods. |
| error_messages | The error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override. |
| validators | The validators argument lets you provide a list of validation functions for this field. |
| localize | The localize argument enables the localization of form data input, as well as the rendered output. |
| disabled. | The disabled boolean argument, when set to True, disables a form field using the disabled HTML attribute so that it won’t be editable by users. |
Please Login to comment…