Django：如何检查用户名是否已经存在？

Question

我不是 Django 的高级用户。我在网上看到了很多不同的方法，但它们都是用于修改模型或太复杂以至于我无法理解。
我在MyRegistrationForm 中重用UserCreationForm

class MyRegistrationForm(UserCreationForm):

    email = forms.EmailField(required=True)

    class Meta:
        model = User
        fields = ('username', 'email', 'password1', 'password2')

    def save(self, commit=True):
        user = super(MyRegistrationForm, self).save(commit=False)
        user.email = self.cleaned_data['email']
        user.set_password(self.cleaned_data["password1"])

        if commit:
            user.save()

        return user

我很难理解或找到一种方法来检查用户输入的用户名是否已被使用。 所以我只是用它来将我重定向到 html，它说错误的用户名或密码不匹配：

def register_user(request):
    if request.method == 'POST':
        form = MyRegistrationForm(request.POST)
        if form.is_valid():
            form.save()

            return HttpResponseRedirect('/accounts/register_success')
        else:
            return render_to_response('invalid_reg.html')
  

    args = {}
    args.update(csrf(request))

    args['form'] = MyRegistrationForm()
    print args
    return render_to_response('register.html', args)

这是我的注册模板（如果需要）：

{% extends "base.html" %}

{% block content %}

<section>
<h2 style="text-align: center">Register</h2>
<form action="/accounts/register/" method="post">{% csrf_token %}

<ul>
{{form.as_ul}}
</ul>
<input type="submit" value="Register" onclick="validateForm()"/>

</form>

</section>
{% endblock %}

但我需要在用户被重定向之前引发某种异常或类似的事情。也许当用户按下注册时，他们会收到错误/警告，说明用户名已被占用。这可能吗？

Answer 1

你可以使用exists:

from django.contrib.auth.models import User

if User.objects.filter(username=self.cleaned_data['username']).exists():
    # Username exists
    ...

Answer 2

您可以使用clean_username 方法检查username 是否存在并引发ValidationError：

def clean_username(self, username):
    user_model = get_user_model() # your way of getting the User
    try:
        user_model.objects.get(username__iexact=username)
    except user_model.DoesNotExist:
        return username
    raise forms.ValidationError(_("This username has already existed."))

如果是这种情况，您可以在注册表单中显示错误，而无需重定向到其他页面。

更新：

根据@Spacedman 指出了一个关于竞争条件的有效点，即针对数据库级别检查表单逻辑上的用户名唯一性，尽管您获得此的机会非常不可能，如果您在这里这样做，相关的 SO 答案可能值得阅读：

How to avoid race condition with unique checks in Django

Race conditions in django

另一个更新

根据 OP 的评论，可以对视图进行另一项更改：

def register_user(request):
    # be DRY, the form can be reused for both POST and GET
    form = MyRegistrationForm(request.POST or None)

    # check both request is a POST and the form is valid
    # as you don't need to redirect for form errors, remove else block
    # otherwise it's going to redirect even form validation fails
    if request.method == 'POST' and form.is_valid():
        form.save()
        return HttpResponseRedirect('/accounts/register_success')
    # I use render so need not update the RequestContext, Django does it for you
    html = render(request, 'register.html', {'form': form})
    return HttpResponse(html)

希望这会有所帮助。

Answer 3

如果您使用的是 django 内置的 Usercreationform，那么只需输入您的模板：

{{form.errors}}

这将检查几乎所有内容，例如：

1. 是否创建了用户
2. 密码是否匹配

Answer 4

我解决了这个问题。

forms.py

from django import forms
from django.contrib.auth.models import User

class RegisterForm(forms.Form):
    username = forms.CharField(max_length=50)
    email = forms.EmailField(required=True)
    password = forms.CharField(widget=forms.PasswordInput())
    confirm = forms.CharField(widget=forms.PasswordInput())

    def clean(self):
        username = self.cleaned_data.get("username")
        email = self.cleaned_data.get("email")
        password = self.cleaned_data.get("password")
        confirm = self.cleaned_data.get("confirm")

        try:
            User._default_manager.get(username=username)
            raise forms.ValidationError("Username already present.Please change          
            username")

        except User.DoesNotExist:


            if username and email and password and confirm and password !=confirm:
                raise forms.ValidationError("Please you check your information")

            values ={
            'username':username,
            'email': email,
            'password':password
           }
            return values

Answer 5

views.py

def register(request):
    form = RegisterForm(request.POST or None)

    if form.is_valid():
        username = form.cleaned_data.get("username")
        email = form.cleaned_data.get("email")
        password = form.cleaned_data.get("password")
        
        newUser = User(username=username,email=email)
                       
            
        newUser.set_password(password)  
        newUser.save()
        messages.success(request,"You're registered successfully")

        return redirect("user:login")    
                       
    return render(request,"signup.html",{"form":form})

Answer 6

你可以使用 unique=True

在models.py中

username = models.CharField(max_length=30, blank=True, null=True, unique=True)