Prerequisites: Django Installation | Introduction to Django
Django works on an MVT pattern. So there is a need to create data models (or tables). For every table, a model class is created.
Suppose there is a form that takes Username, gender, and text as input from the user, the task is to validate the data and save it.
In django this can be done, as follows:
Python
from django.db import models # model named Post class Post(models.Model): Male = 'M' FeMale = 'F' GENDER_CHOICES = ( (Male, 'Male' ), (FeMale, 'Female' ), ) # define a username field with bound max length it can have username = models.CharField( max_length = 20 , blank = False , null = False ) # This is used to write a post text = models.TextField(blank = False , null = False ) # Values for gender are restricted by giving choices gender = models.CharField(max_length = 6 , choices = GENDER_CHOICES, default = Male) time = models.DateTimeField(auto_now_add = True ) |
After creating the data models, the changes need to be reflected in the database to do this run the following command:
python manage.py makemigrations
Doing this compiles the models and if it didn’t find any errors then, it creates a file in the migration folder. Later run the command given below to finally reflect the changes saved onto the migration file onto the database.
python manage.py migrate
Now a form can be created. Suppose that the username length should not be less than 5 and post length should be greater than 10. Then we define the Class PostForm with the required validation rules as follows:
Python
from django.forms import ModelForm from django import forms from formValidationApp.models import * # define the class of a form class PostForm(ModelForm): class Meta: # write the name of models for which the form is made model = Post # Custom fields fields = [ "username" , "gender" , "text" ] # this function will be used for the validation def clean( self ): # data from the form is fetched using super function super (PostForm, self ).clean() # extract the username and text field from the data username = self .cleaned_data.get( 'username' ) text = self .cleaned_data.get( 'text' ) # conditions to be met for the username length if len (username) < 5 : self ._errors[ 'username' ] = self .error_class([ 'Minimum 5 characters required' ]) if len (text) < 10 : self ._errors[ 'text' ] = self .error_class([ 'Post Should Contain a minimum of 10 characters' ]) # return any errors if found return self .cleaned_data |
Till now, the data models and the Form class are defined. Now the focus will be on how these modules, defined above, are actually used.
First, run on localhost through this command
python manage.py runserver
Open http://localhost:8000/ in the browser, then it’s going to search in the urls.py file, looking for ‘ ‘ path
urls.py file is as given below:
Python
from django.contrib import admin from django.urls import path, include from django.conf.urls import url from django.shortcuts import HttpResponse from . import views urlpatterns = [ path(' ', views.home, name =' index'), ] |
Basically, this associates the ‘ ‘ url with a function home which is defined in views.py file.
views.py file:
Python
from .models import Post from .forms import PostForm from . import views from django.shortcuts import HttpResponse, render, redirect def home(request): # check if the request is post if request.method = = 'POST' : # Pass the form data to the form class details = PostForm(request.POST) # In the 'form' class the clean function # is defined, if all the data is correct # as per the clean function, it returns true if details.is_valid(): # Temporarily make an object to be add some # logic into the data if there is such a need # before writing to the database post = details.save(commit = False ) # Finally write the changes into database post.save() # redirect it to some another page indicating data # was inserted successfully return HttpResponse( "data submitted successfully" ) else : # Redirect back to the same page if the data # was invalid return render(request, "home.html" , { 'form' :details}) else : # If the request is a GET request then, # create an empty form object and # render it into the page form = PostForm( None ) return render(request, 'home.html' , { 'form' :form}) |
home.html template file
html
{% load bootstrap3 %} {% bootstrap_messages %} <!DOCTYPE html> < html lang = "en" > < head > < title >Basic Form</ title > < meta charset = "utf-8" /> < meta name = "viewport" content = "width=device-width, initial-scale=1, shrink-to-fit=no" > < link rel = "stylesheet" href = "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" > </ script > </ script > </ head > < body style = "padding-top: 60px;background-color: #f5f7f8 !important;" > < div class = "container" > < div class = "row" > < div class = "col-md-4 col-md-offset-4" > < h2 >Form</ h2 > < form action = "" method = "post" >< input type = 'hidden' /> {%csrf_token %} {% bootstrap_form form %} <!-This is the form variable which we are passing from the function of home in views.py file. That's the beauty of Django we don't need to write much codes in this it'll automatically pass all the form details in here -> < div class = "form-group" > < button type = "submit" class = "btn btn-default " > Submit </ button > </ div > </ form > </ div > </ div > </ div > </ body > </ html > |
Opening http://localhost:8000/ in the browser shows the following,
If a form with a username of length less than 5 is submitted, it gives an error at the time of submission and similarly for the Post Text filled as well. The following image shows how the form behaves on submitting invalid form data.