用 django 形式保存新的外键 [英] Save new foreign key with django form

问题描述

我有两个模型:

class Studio(models.Model):
    name = models.CharField("Studio", max_length=30, unique=True)

class Film(models.Model):
    studio = models.ForeignKey(Studio, verbose_name="Studio")
    name = models.CharField("Film Name", max_length=30, unique=True)

我有一个电影表单，允许用户选择一个预先存在的工作室，或者输入一个新的:

I have a Film form that allows the user to either select a preexisting Studio, or type in a new one:

class FilmForm(forms.Form):
    studio = forms.ModelChoiceField(Studio.objects, required=False)
    new_studio = forms.CharField(max_length=30, required=False, label = "New Studio Name")
    name = forms.CharField(max_length=30, label = "Film Name")

有验证以确保 new_studio 名称不存在.如果用户输入new_studio，我想保存工作室，然后保存新的Film.

There's validation to assure that the new_studio name doesn't already exist. If the user enters a new_studio, I want to save the studio and then save the new Film.

form = FilmForm(request.POST) 
if form.is_valid(): # All validation rules pass
    std = Studio(name = form.cleaned_data['new_studio'])
    std.save()

但是，我如何将 Film 实例保存到全新的工作室 ID 之下?我已经看过这个问题，但是如果我在 Film 模型中有更多字段并且电影形式?如果我使用链接的答案，则必须输入每个字段:

But then how do I save the Film instance subject to the brand new studio id? I've seen this question, but what if I have many more fields in the Film model and Film Form? If I use the linked answer, I would have to enter each field:

studio = Studio.objects.get(name=request.POST['new_studio'])
newFilm=Film(name=form.name, studio=studio, field_one = form.field_one, field_two = form.field_two, etc.)

实现这一点的正确方法是什么?

What is the correct way to implement this?

推荐答案

实际上，您唯一的问题是您使用了标准的 Form 而不是 ModelForm.Form 没有 save 方法，因为它本身并不与任何东西相关联(即它不知道要保存什么或保存到哪里).

Really, your only problem is that you've used a standard Form instead of a ModelForm. Form doesn't have a save method because it's not inherently tied to anything (i.e. it doesn't know what to save or where to save to).

但是，如果您使用 ModelForm，您需要处理在表单中创建新工作室所涉及的所有逻辑.不过，这实际上更好，因为这样您就可以只使用表单而不必担心其他任何事情:表单包含正确保存自身所需的所有逻辑.

However, if you use a ModelForm you need to take care of all logic involved in creating a new studio in the form. This is actually better, though, because then you can just use the form and not worry about anything else: the form holds all the logic needed to properly save itself.

class FilmForm(forms.ModelForm):
    class Meta:
        model = Film

    # only need to define `new_studio`, other fields come automatically from model
    new_studio = forms.CharField(max_length=30, required=False, label = "New Studio Name")

    def __init__(self, *args, **kwargs):
        super(FilmForm, self).__init__(*args, **kwargs)
        # make `studio` not required, we'll check for one of `studio` or `new_studio` in the `clean` method
        self.fields['studio'].required = False

    def clean(self):
        studio = self.cleaned_data.get('studio')
        new_studio = self.cleaned_data.get('new_studio')
        if not studio and not new_studio:
            # neither was specified so raise an error to user
            raise forms.ValidationError('Must specify either Studio or New Studio!')
        elif not studio:
            # get/create `Studio` from `new_studio` and use it for `studio` field
            studio, created = Studio.objects.get_or_create(name=new_studio)
            self.cleaned_data['studio'] = studio

        return super(FilmForm, self).clean()

那么，在您看来，您只需要:

Then, in your view, all you need is:

if form.is_valid():
    form.save()

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