Django之ModelForm使用

一：什么是ModelForm呢？

Model + Form ==> ModelForm。model和form的结合体，所以有以下功能：

• 数据验证
• 数据库操作

model有操作数据库的字段，form验证也有那几个字段，虽然耦合度降低，但是代码是有重复的。如果利用model里的字段，那是不是form里的字段就不用写了。

二：下面是一个简单是例子：

from django.db import models

class CustomerInfo(models.Model):
    """客户表"""
    name = models.CharField(max_length=64)
    contact_type_choices = ((0,'QQ'),(1,'微信'),(2,'手机'))
    contact_type = models.SmallIntegerField(choices=contact_type_choices)
    contact = models.CharField(max_length=64,unique=True,verbose_name="联系方式")
    source_choices = ((0,'QQ群'),(1,'51CTO'),(2,'百度推广'),(3,'知乎'),(4,'转介绍'),(5,'其它'))
    source = models.SmallIntegerField(choices=source_choices,verbose_name="客户来源")
    referral_from = models.ForeignKey("self",blank=True,null=True,verbose_name="转介绍",on_delete=models.CASCADE)
    consult_courses = models.ManyToManyField("Course",verbose_name="咨询课程")
    consult_content = models.TextField(verbose_name="咨询内容")
    status_choices = ((0, '未报名'), (1, '已报名'), (2, '已退学'))
    status = models.SmallIntegerField(choices=status_choices,verbose_name="状态")
    consultant = models.ForeignKey("UserProfile",verbose_name="课程顾问",on_delete=models.CASCADE)
    date = models.DateField(auto_now_add=True)
    def __str__(self):
        return self.name

from django.forms import ModelForm
from crm import models
from django import forms

class CustomerForm(ModelForm):
    class Meta:
        model = models.CustomerInfo
        fields = '__all__'
        exclude = ['consult_content', 'status', 'consult_courses']
        readonly_fields = ['contact_type','contact','consultant','referral_from','source']   #并不是真正的设置可读模式，而是用于自定制

    def __new__(cls, *args, **kwargs):      # cls 就是实例(self)
        for field_name in cls.base_fields:
            field_obj = cls.base_fields[field_name]
            field_obj.widget.attrs.update({'class':'form-control'})
            if field_name in cls.Meta.readonly_fields:
                field_obj.widget.attrs.update({'disabled':'true'})
                # print(cls.Meta)
        # print(cls.Meta.exclude)
        return ModelForm.__new__(cls)

    def clean(self):
        """对数据进行验证，此方法需要在form.is_valid()后才能生效"""
        # print("cleaned_dtat:", self.cleaned_data)
        if self.errors:  # 表单级别的错误
            raise forms.ValidationError(("Please fix errors before re-submit."))
        for field in self.Meta.readonly_fields:
            old_field_val = getattr(self.instance,field)
            new_form_val = self.cleaned_data[field]
            if old_field_val != new_form_val:
                self.add_error(field,"Readonly Field: field should be '{value}' ,not '{new_value}' ".
                                         format(**{'value':old_field_val,'new_value':new_form_val}))

def enrollment(request,enrollment_id):
    """②学员确认信息"""
    customer_form = forms.CustomerForm(instance=enrollment_obj.customer)
    
    if request.method == "POST":
        customer_form = forms.CustomerForm(instance=enrollment_obj.customer,data=request.POST)
        if customer_form.is_valid():
            customer_form.save()
            return HttpResponse('合同正在审核中，请等候...')

    return render(request,'crm/enrollment.html',locals())

注意我们如何在POST和GET情况下传递实例（instance）。

三、Meta的作用：

• ModelForm 通过 Meta 把 db.Field 自动转化为 forms.Field，其中涉及到几步转化
• validators 不变
• 添加 widget 属性，即前端的渲染方式
• 修改 Model 包含的字段，通过 fields 来拿指定字段或者通过 exclude 来排除指定字段
• 修改错误信息

class Meta:
        model = models.UserInfo
        fields = '__all__'
        # fields =  ['username','email']
        # exclude = ['username']
        labels = {
            'username': '用户名',
            'email': '邮箱',
        }
        help_texts = {
            'username': '...'
        }
        widgets = {
            'username': Fwidgets.Textarea(attrs={'class': 'c1'})
        }
        error_messages = {
            '__all__':{
 
            },
            'email': {
                'required': '邮箱不能为空',
                'invalid': '邮箱格式错误..',
            }
        }
        field_classes = {
            # 'email': Ffields.URLField
        }
 
        # localized_fields=('ctime',)