Python|使用 django 进行表单验证

先决条件：Django 安装 | Django 简介
Django 使用 MVT 模式。因此需要创建数据模型（或表）。对于每个表，都会创建一个模型类。
假设有一个表单将用户名、性别和文本作为用户的输入，任务是验证数据并保存。
在 django 中可以这样做，如下所示：

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 filed 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)

创建数据模型后，需要在数据库中反映更改以执行此操作，请运行以下命令：

python manage.py makemigrations

这样做会编译模型，如果没有发现任何错误，则会在迁移文件夹中创建一个文件。稍后运行下面给出的命令，最终将保存到迁移文件中的更改反映到数据库中。

python manage.py migrate

现在可以创建一个表单。假设用户名长度不应小于 5，post 长度应大于 10。那么我们使用所需的验证规则定义PostForm类，如下所示：

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

至此，数据模型和Form类已经定义完毕。现在的重点将放在如何实际使用上面定义的这些模块。
首先，通过这个命令在 localhost 上运行

python manage.py runserver

在浏览器中打开http://localhost:8000/ ，然后它会在urls.py文件中搜索，寻找''路径
urls.py文件如下所示：

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'),
]

基本上，这会将 ' ' url 与在views.py文件中定义的函数主页相关联。
view.py 文件：

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模板文件

html

{% load bootstrap3 %}
{% bootstrap_messages %}


 

 
    Basic Form
     
    
     
    
 






 

    
    
        
        Form
             
             {%csrf_token %}
 
                {% bootstrap_form form %}

              
                
                  Submit
                
 
                  
 
                
        
    

 

 

在浏览器中打开http://localhost:8000/显示如下，

如果提交了一个用户名长度小于 5 的表单，它会在提交时出错，对于填写的 Post Text 也是如此。下图显示了表单在提交无效表单数据时的行为。