Django中使用CreateView在表单无效时显示错误消息的问题

方法一：在表单类中添加验证逻辑（推荐） #

将名称验证逻辑放到ProjectForm中，符合Django表单验证的最佳实践，代码更清晰易维护：

from django import forms
from .models import Project

class ProjectForm(forms.ModelForm):
    class Meta:
        model = Project
        fields = ['name', 'creation_date', 'price']

    def clean_name(self):
        name = self.cleaned_data.get('name')
        if name == "not_valid_name":
            raise forms.ValidationError("名称无效")
        return name


class ProjectCreate(LoginRequiredMixin, SuccessMessageMixin, CreateView):
    model = Project
    form_class = ProjectForm
    success_message = "Project successfully created"
    success_url = "project-list"

    def get_form(self, form_class=None):
        form = super().get_form(form_class)
        form.fields.pop('creation_date')
        return form

    def form_valid(self, form):
        form.instance.last_editor = self.request.user
        form.instance.last_modification_date = datetime.datetime.now()
        return super().form_valid(form)

方法二：在视图的form_valid方法中处理 #

如果一定要在视图层处理，需要手动将错误信息添加到表单的name字段，再返回form_invalid：

from django import forms
from django.views.generic.edit import CreateView
from django.contrib.auth.mixins import LoginRequiredMixin
from django.contrib.messages.views import SuccessMessageMixin
from .models import Project
import datetime

class ProjectForm(forms.ModelForm):
    class Meta:
        model = Project
        fields = ['name', 'creation_date', 'price']


class ProjectCreate(LoginRequiredMixin, SuccessMessageMixin, CreateView):
    model = Project
    form_class = ProjectForm
    success_message = "Project successfully created"
    success_url = "project-list"

    def get_form(self, form_class=None):
        form = super().get_form(form_class)
        form.fields.pop('creation_date')
        return form

    def form_valid(self, form):
        if form.instance.name == "not_valid_name":
            # 添加错误信息到name字段
            form.add_error('name', "名称无效")
            return self.form_invalid(form)
        form.instance.last_editor = self.request.user
        form.instance.last_modification_date = datetime.datetime.now()
        return super().form_valid(form)

说明 #

• 方法一中，clean_name方法是Django表单的字段级验证方法，会在表单验证阶段自动执行，验证失败时抛出的ValidationError会被自动渲染到表单的对应字段下方。
• 方法二中，通过form.add_error('name', "名称无效")手动添加错误信息，再调用form_invalid返回表单页面，这样用户就能看到自定义的错误提示。

内容的提问来源于stack exchange，提问作者Alexandre Boucard