如何更改 Django ModelForm 中的数据？

Question

models.py

class Playlist(models.Model):
    name = models.CharField(max_length=50)
    num_of_songs = models.IntegerField(max_length=15)
    duration = models.IntegerField()
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True)
    songs = models.ManyToManyField("Song", blank=True)

forms.py

class PlaylistEditForm(forms.ModelForm):
    class Meta:
        model = Playlist
        fields = ['name', 'songs']

我根据从表格中得到的歌曲计算duration和num_of_songs。但我是从一个角度计算的。

views.py

playlist = Playlist.objects.get(id=playlist_id)

if request.method == 'POST':
    form = PlaylistEditForm(request.POST, instance=playlist)
    if form.is_valid():
        form.save()
        playlist.duration = playlist.songs.aggregate(Sum('duration'))['duration__sum'] or 0
        playlist.num_of_songs = playlist.songs.count()
        playlist.save()

我想在表格中计算 duration 和 num_of_songs。

Answer 1

有什么理由不在模型 save() 方法中这样做吗？如果你在表单 save() 方法中有它，如果你保存模型实例而不是来自模型表单的模型实例，数据库中的持续时间和 num_of_songs 将不会更新。

class Playlist(models.Model):
    name = models.CharField(max_length=50)
    num_of_songs = models.IntegerField(max_length=15)
    duration = models.IntegerField()
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True)
    songs = models.ManyToManyField("Song", blank=True)

    def save(self, *args, **kwargs):
        if self.pk:
            self.duration = self.songs.aggregate(Sum('duration'))['duration__sum'] or 0
            self.num_of_songs = self.songs.count()
        return super(Playlist, self).save(*args, **kwargs)

您的观点是：

if request.method == 'POST':
    form = PlaylistEditForm(request.POST, instance=playlist)
    if form.is_valid():
        playlist = form.save()

Answer 2

您可以将计算移动到覆盖表单的 save 方法的表单中

def save(self, commit=True):
    instance = super(PlaylistEditForm, self).save(commit=False)
    instance.duration = instance.songs.aggregate(Sum('duration'))['duration__sum'] or 0
    instance.num_of_songs = instance.songs.count()
    if commit:
        instance.save()
    return instance

你的视图变成

playlist = Playlist.objects.get(id=playlist_id)

if request.method == 'POST':
    form = PlaylistEditForm(request.POST, instance=playlist)
    if form.is_valid():
        form.save()

请参阅 Django 的 official docs 了解更多信息。

如何更改 Django ModelForm 中的数据？

How to change data in Django ModelForm?

python

django

django-models

django-forms