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如何为ForeignKey使用默认字段值?

django python

Andrew · 技术社区 · 4 年前

我刚刚开始学习Django并用它建立一个简单的博客。所以我有两个模型 Post 和 PostStatistics 。每当我添加新帖子时,我希望PostStatistics包含所有指定的默认值。我怎样才能正确地做到这一点?

模型。py

class PostStatistics(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid4)
    post_views = models.IntegerField(default=0)
    post_likes = models.IntegerField(default=0)
    post_favorites = models.IntegerField(default=0)

class Post(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid4)
    user = models.ForeignKey(UserProfile, null=True, on_delete=models.CASCADE)
    statistics = models.ForeignKey(PostStatistics, null=True, on_delete=models.CASCADE)
    title = models.CharField(max_length=200)
    body = RichTextField(blank=True, null=True)
    draft = models.BooleanField(default=False)

意见。py

def add_post(request: HttpRequest):
    form = PostForm(request.POST)
    is_draft = True if form.data.get("draft") == "on" else False
    post = Post(
        title=form.data["title"],
        body=form.data["post"],
        user=request.user,
        draft=is_draft,
        statistics = PostStatistics() -> this is not correct
    )
    post.save()
    return redirect("post")

在我得到 FOREIGN KEY constraint failed .

1 回复 | 直到 4 年前

willeM_ Van Onsem 4 年前

创建一个新的:

def add_post(request: HttpRequest):
    form = PostForm(request.POST)
    is_draft = form.data.get('draft') == 'on'
    post_statistics = PostStatistics.objects.create()
    Post.objects.create(
        title=form.data['title'],
        body=form.data['post'],
        user=request.user,
        draft=is_draft,
        statistics = post_statistics
    )
    return redirect('post')

然而,将统计数据存储在单独的模型中没有多大意义,因为存在明确的一对一关系,因此统计数据可以存储在单独的模型中 Post 模型

此外,还可以使用表单验证输入,并创建对象(或至少部分对象)。因此,更好的建模方法可能是:

from django.conf import settings

class Post(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid4)
    user = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, on_delete=models.CASCADE, editable=False)
    title = models.CharField(max_length=200)
    body = RichTextField(blank=True, null=True)
    draft = models.BooleanField(default=False)
    post_views = models.IntegerField(default=0, editable=False)
    post_likes = models.IntegerField(default=0, editable=False)
    post_favorites = models.IntegerField(default=0, editable=False)

然后和一个 ModelForm 让表格进行所有适当的验证和清理:

from django.contrib.auth.decorators import login_required

@login_required
def add_post(request: HttpRequest):
    if request.method == 'POST':
        form = PostForm(request.POST)
        if form.is_valid():
            form.instance.user = request.user
            form.save()
            return redirect('post')
    else:
        form = PostForm()
    return render(request, 'name-of-some-template.html', {'form': form})

笔记 :通常最好利用 settings.AUTH_USER_MODEL Â ^[Django-doc] 参考用户模型,而不是使用 User modelÂ ^[Django-doc] 直接地有关更多信息,请参见 referencing the User model section of the documentation .

笔记 :您可以将视图限制为具有 @login_required decoratorÂ ^[Django-doc] .