优化Django表单：提交验证失败后保留用户输入

<input class="form-control" type="text" name="first_name" placeholder="Firstname" required>

# your_app/forms.py
from django import forms
from django.contrib.auth.forms import UserCreationForm
from .models import UserModel # 假设你有一个UserModel

class CustomUserCreationForm(UserCreationForm):
    first_name = forms.CharField(
        label='',
        widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Firstname'})
    )
    last_name = forms.CharField(
        label='',
        widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Lastname'})
    )
    email = forms.CharField(
        label='',
        widget=forms.EmailInput(attrs={'class': 'form-control', 'placeholder': 'Email address'})
    )
    password1 = forms.CharField(
        label='',
        widget=forms.PasswordInput(attrs={'class': 'form-control', 'placeholder': 'Enter Password'})
    )
    password2 = forms.CharField(
        label='',
        widget=forms.PasswordInput(attrs={'class': 'form-control', 'placeholder': 'Confirm your password'})
    )

    class Meta:
        model = UserModel
        fields = ('email', 'first_name', 'last_name') # 注意这里只包含ModelForm要处理的字段
                                                      # password1和password2通常在clean方法中处理

    # 可选：自定义验证逻辑，例如密码匹配
    def clean(self):
        cleaned_data = super().clean()
        password_1 = cleaned_data.get('password1')
        password_2 = cleaned_data.get('password2')

        if password_1 and password_2 and password_1 != password_2:
            self.add_error('password2', "Passwords do not match.") # 为特定字段添加错误
        return cleaned_data

# your_app/views.py
from django.shortcuts import render, redirect
from django.contrib.auth import login
from django.contrib import messages
from .forms import CustomUserCreationForm # 导入你的表单

def register_view(request):
    if request.method == 'POST':
        form = CustomUserCreationForm(request.POST) # 绑定提交的数据
        if form.is_valid():
            user = form.save()
            login(request, user)
            messages.success(request, f'{user.first_name}, your account has been created successfully')
            return redirect('home') # 假设你有一个名为'home'的URL
        else:
            # 如果验证失败，form实例仍然包含用户提交的数据和错误信息
            # 此时，form会被再次渲染，并自动填充之前的数据
            # messages.error(request, form.errors) # 可以选择显示所有错误，或在模板中逐个显示
            pass # 错误将在模板中显示
    else:
        form = CustomUserCreationForm() # GET请求，创建空表单

    return render(request, 'base/register.html', {'form': form})

<!-- base/register.html -->
<form method="POST" class="requires-validation" novalidate>
    {% csrf_token %} {# 重要的安全措施 #}

    <div class="col-md-12">
        {# 渲染first_name字段，Django会自动处理value属性 #}
        {{ form.first_name.label_tag }} {# 可选：显示字段标签 #}
        {{ form.first_name }}
        {% if form.first_name.errors %}
            {% for error in form.first_name.errors %}
                <span style="color:#DC3545;">{{ error }}</span>
            {% endfor %}
        {% endif %}
    </div>

    <div class="col-md-12">
        {{ form.last_name.label_tag }}
        {{ form.last_name }}
        {% if form.last_name.errors %}
            {% for error in form.last_name.errors %}
                <span style="color:#DC3545;">{{ error }}</span>
            {% endfor %}
        {% endif %}
    </div>

    <div class="col-md-12">
        {{ form.email.label_tag }}
        {{ form.email }}
        {% if form.email.errors %}
            {% for error in form.email.errors %}
                <span style="color:#DC3545;">{{ error }}</span>
            {% endfor %}
        {% endif %}
    </div>

    <div class="col-md-12">
        {{ form.password1.label_tag }}
        {{ form.password1 }}
        {% if form.password1.errors %}
            {% for error in form.password1.errors %}
                <span style="color:#DC3545;">{{ error }}</span>
            {% endfor %}
        {% endif %}
    </div>

    <div class="col-md-12">
        {{ form.password2.label_tag }}
        {{ form.password2 }}
        {% if form.password2.errors %}
            {% for error in form.password2.errors %}
                {# 自定义错误信息，或者使用{{ error }}显示Django默认的 #}
                <span style="color:#DC3545;">Passwords do not match, confirm and try again</span>
            {% endfor %}
        {% endif %}
    </div>

    <div class="form-button mt-3">
        <button id="submit" type="submit" class="btn btn-primary">Register</button>
    </div>
    <br>
    <span>Already have an account?<a href=""> Sign in</a></span>
</form>