管理界面的动态选择项

Question

我想创建一个级联的父子选择器，也就是说，子选项是根据父选项来决定的。选项是从预先定义的变量或JSON中获取的。用户需要先选择父选项，才能看到对应的子选项。所以，默认情况下，子选项是没有任何选项的。

我在管理表单中使用了Ajax来填充子选项，但是当模型被保存后，子选项又回到了最初的状态，也就是没有任何选项。

#choices
PARENT = {
    ('1','Parent 1'),
    ('2','Parent 2'),
    ('3', 'Parent 3'),
}
CHILD_CHOICES = {
    '1' : (("c1-opt1","Option 1-1"),("c1-opt2","Child option 1-2"),("c1-opt3","Child option 1-3")),
    '2' : (("c2-opt1","Option 2-1"),("c2-opt2","Child option 2-2"),("c2-opt3","Child option 2-3")),
    '3' : (("c3-opt1","Option 3-1"),("c2-opt3","Child option 3-2"),("c2-opt3","Child option 3-3"))
}
#model.py
class Relation(models.Model)
parent = models.CharField(max_length=4,choices=Parent,blank=True)
child = models.CharField(max_length=200)

我知道可以在admin.py中自定义“子”字段，但我不知道如何在页面加载时根据保存的模型父字段来填充选项。

#admin.py
class Cascadingform(forms.ModelForm):
    class Meta:
        model = Relation

    def __init__(self,  *args, **kwargs):
    super(Cascadingform, self).__init__(*args, **kwargs)
    if(self.parent): #not sure how to get the parent value here
        self.fields['child'] = forms.Select(choices=CHILD_CHOICES[self.parent])#  populated the choice based on the dict above. 

我的问题是，我能否在init中获取“父”值，以便用它来填充子选项？有什么想法吗？

Answer 1

经过几天的搜索，这就是我的解决办法：

def getFieldChoices(parent):
    CHILD_CHOICES = {
'1' : (("c1-opt1","Option 1-1"),("c1-opt2","Child option 1-2"),("c1-opt3","Child option 1-3")),
'2' : (("c2-opt1","Option 2-1"),("c2-opt2","Child option 2-2"),("c2-opt3","Child option 2-3")),
'3' : (("c3-opt1","Option 3-1"),("c2-opt3","Child option 3-2"),("c2-opt3","Child option 3-3"))}
    L = list()
    data = CHILD_CHOICES.get(parent, None)
    if data:
        L = [[x, x] for x in data]    
    return L


#admin.py
class Cascadingform(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(Cascadingform, self).__init__(*args,**kwargs)

        if (self.instance.parent):
            self.fields['child'] = forms.CharField(widget=forms.Select(attrs={'class':'childclass'},choices=getFieldChoices(self.instance.parent))
                            )
        else:
            self.fields['child'] = forms.CharField(widget=forms.Select(attrs={'class':'childclass'},choices=[('','Select Parent First'),])
                            )
    class Meta:
        model = Relation