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）
  

一个电影表单，允许用户选择一个预先存在的工作室，或输入一个新的：

  class FilmForm（forms。表单）
 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 =电影名称）
  

确保new_studio名称不存在。如果用户输入new_studio，我想保存工作室，然后保存新的电影。

  form = FilmForm（request.POST）
如果form.is_valid（）：＃所有验证规则通过
 std = Studio（name = form.cleaned_data ['new_studio']）
 std.save（）
  

但那么如何保存电影实例受制于全新的工作室标识？我已经看到这个问题，但是如果我在电影模型中有更多的领域，电影表格？如果我使用链接的答案，我必须输入每个字段：

  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等）
  

实现这一点的正确方法是什么？

解决方案>

真的，您唯一的问题是您使用了标准的表单而不是 ModelForm 。 表单没有保存方法，因为它并不固有地绑定到任何东西（即它不知道什么保存或保存到哪里）

但是，如果您使用 ModelForm ，则需要照顾所有在形式上创建一个新的工作室的逻辑。这实际上是更好的，因为那样你就可以使用表单，而不用担心别的东西：表单包含正确保存自己所需的所有逻辑。

  class FilmForm（forms.ModelForm）：
 class Meta：
 model = Film 
 
＃只需要定义`new_studio`，其他字段来自动从模型
 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`不需要，我们将检查`studio`或`new_studio`中的`clean `方法
 self.fields ['studio']。required = False 
 
 def clean（self）：
 studio = self.cleaned_data.get（'studio'）
 new_studio = self.cleaned_data.get（'new_studio'）
如果不是studio而不是new_studio：
＃没有指定这样引用对于用户
 raise forms.ValidationError（'必须指定Studio或New Studio！'）的错误
 elif not studio：
＃从`new_studio`创建`Studio`并使用它为`studio`字段
 studio，created = Studio.objects.get_or_create（name = new_studio）
 self.cleaned_data ['studio'] = studio 
 
 return super（FilmForm ，self）.clean（）
  

然后，在你看来，你需要的是：

  if form.is_valid（）：
 form.save（）
  pre> 
I have two models:
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)
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")
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()
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.)
What is the correct way to implement this?
解决方案
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).

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()
Then, in your view, all you need is:
if form.is_valid():
    form.save()


                        
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