这两种使用表单更新数据库的方法有什么区别？

Question

我正在尝试使用表单更新数据库。我想 select 下拉列表中的标题，并更新 'opening_crawl' 字段以从文本区域输入。

models.py :

class Movies(models.Model):

    episode_nb = models.IntegerField(primary_key=True)
    title = models.CharField(max_length=64, unique=True, null=False)
    opening_crawl = models.TextField(null=True)
    director = models.CharField(max_length=32)
    producer = models.CharField(max_length=128)
    release_date = models.DateField()
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True, editable=True)

forms.py:

class TitleDropDownForm(forms.Form):
    title = forms.ModelChoiceField(queryset=Movies.objects.only('title'), empty_label=None)
    opening_crawl = forms.CharField(widget=forms.Textarea)

views.py:

def update(request):
    msg = ''
    if request.method == 'POST':
        form = TitleDropDownForm(request.POST)
        if form.is_valid():
        
            #method 1 : it updates 'opening_crawl' properly, but not 'updated_time'.
            movie = form.cleaned_data['title']
            movie.opening_crawl = form.cleaned_data['opening_crawl']
            movie.save()    



        #method 2
        #h = Movies.objects.get(pk=1)
        #h.opening_crawl = 'HAND WRITTEN MESSAGE!'
        #h.save()


        return redirect(request.META.get('HTTP_REFERER'))
    else:
        form = TitleDropDownForm()
    if not form.fields['title'].queryset:
        msg = 'No data available.'

    return render(request, 'ex07/update.html', context={'form' : form, 'msg' : msg})

方法 1 适用于 'opening_crawl' 字段，但 'updated' 日期时间字段未更改。当我像方法 2 一样尝试时，它会正确更新两个字段。两种方法有什么区别？有什么误会吗？

Answer 1

我怀疑是因为你在使用 .only()

来自Django documentation：

When saving a model fetched through deferred model loading (only() or defer()) only the fields loaded from the DB will get updated. In effect there is an automatic update_fields in this case. If you assign or change any deferred field value, the field will be added to the updated fields.

在第二种方法中，您将获得整个模型，没有任何延迟字段（即 updated）

这两种使用表单更新数据库的方法有什么区别？

What is difference between these two method of updating DB using form?

django

django-models

django-forms