“无法在没有主键的情况下强制save()中的更新"-提交编辑/更新表单时 [英] "Cannot force an update in save() with no primary key"- when submitting an edit/update form

问题描述

我有一个编辑表单，我只想更新帖子的标题"，内容"和类别".为此，我在保存表单时加入了 update_fields .但是，这有一个令人毛骨悚然的问题.当我提交表单时，Django会引发ValueError(特别是无法在没有主键的情况下强制save()中进行更新").为什么这样做，我该如何解决?

I have an edit form that I only want to update the "title", "content", and "category" of a Post. To this end, I have included update_fields when saving the form. However, there's a wee issue with this. Django raises a ValueError (specifically "Cannot force an update in save() with no primary key") when I submit the form. Why is it doing this, and how can I fix this?

发布表格:

class PostForm(forms.ModelForm):

    def __init__(self,  *args, **kwargs):
        super().__init__(*args, **kwargs)
        for key in ['postTitle', 'postContent', 'category']:
            self.fields[key].widget.attrs.update({'class': 'form-control'})         
        self.fields['content'].widget.attrs.update(width='100px', height='50')

    class Meta:
        model = Post
        fields = ('title', 'content', 'category') 

发布模型:

class Post(models.Model):
    title = models.CharField(max_length = 100)
    URL = models.SlugField() # slug for url 
    content = models.TextField()
    author = models.ForeignKey(User, on_delete = models.CASCADE, related_name = 'posts') # id of author
    category = models.CharField(max_length = 9, default = 'General') # category the post is in
    creationDate = models.DateTimeField()

编辑视图:

def editPost(request, pk):
    if request.method == 'GET':
        post = get_object_or_404(Post, pk = pk)
        if post.author == request.user:
            form = PostForm(instance = post)
            return render(request, 'editPost.html',  {'form': form, 'post': post})
        else:
            return redirect('viewPost', pk = pk, postURL = post.postURL)
    if request.method == 'POST':
        post = get_object_or_404(Post, pk = pk)
        form = PostForm(request.POST)
        if post.author == request.user:
            if form.is_valid():
                post = form.save(commit=False)
                post.URL = slugify(post.postTitle)
                post.save(update_fields = ['title', 'content', 'category', 'postURL'])
    return redirect('viewAll')

推荐答案

似乎您正在此处重新分配帖子.在这一行；

Seems like you are re-assigning post here. In this line;

post = get_object_or_404(Post, pk = pk)

您正在从数据库中获取Post实例.然后在这一行；

You are getting a Post instance from the database. Then in this line;

post = form.save(commit=False)

您正在将post变量重新分配给一个Post的未保存实例，该实例仅填充request.POST中可用的数据.然后，当您想使用 update_fields 这样的参数保存帖子时:

You are re-assigning post variable to an unsaved instance of a Post, populated with only the data that is available in request.POST. Then, when you want to save this post with an update_fields argument like this:

post.save(update_fields = ['title', 'content', 'category', 'postURL'])

出现

ValueError的原因是，您要保存的Post实例没有ID，仅具有 request.POST

这篇关于“无法在没有主键的情况下强制save()中的更新"-提交编辑/更新表单时的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！