Django ModelForm用于多对多字段

Django ModelForm用于多对多字段

我想你会在这里新添加

ModelMultipleChoiceField

到你

PizzaForm

，并手动链接，表单字段与模型领域，如Django会不会为你做自动。

以下代码段可能会有所帮助：

class PizzaForm(forms.ModelForm):    class meta:        model = Pizza    # Representing the many to many related field in Pizza    toppings = forms.ModelMultipleChoiceField(queryset=Topping.objects.all())    # Overriding __init__ here allows us to provide initial    # data for 'toppings' field    def __init__(self, *args, **kwargs):        # only in case we build the form from an instance        # (otherwise, 'toppings' list should be empty)        if kwargs.get('instance'): # We get the 'initial' keyword argument or initialize it # as a dict if it didn't exist.      initial = kwargs.setdefault('initial', {}) # The widget for a ModelMultipleChoiceField expects # a list of primary key for the selected data. initial['toppings'] = [t.pk for t in kwargs['instance'].topping_set.all()]        forms.ModelForm.__init__(self, *args, **kwargs)    # Overriding save allows us to process the value of 'toppings' field        def save(self, commit=True):        # Get the unsave Pizza instance        instance = forms.ModelForm.save(self, False)        # Prepare a 'save_m2m' method for the form,        old_save_m2m = self.save_m2m        def save_m2m():old_save_m2m()# This is where we actually link the pizza with toppingsinstance.topping_set.clear()instance.topping_set.add(*self.cleaned_data['toppings'])        self.save_m2m = save_m2m        # Do we need to save all changes now?        if commit: instance.save() self.save_m2m()        return instance

这

PizzaForm

然后可以使用无处不在，甚至在admin：

# yourapp/admin.pyfrom django.contrib.admin import site, ModelAdminfrom yourapp.models import Pizzafrom yourapp.forms import PizzaFormclass PizzaAdmin(ModelAdmin):  form = PizzaFormsite.register(Pizza, PizzaAdmin)

注意

该

save()

方法可能有点过于冗长，但是如果你不需要支持这种

commit=False

情况，则可以将其简化，如下所示：

def save(self):  instance = forms.ModelForm.save(self)  instance.topping_set.clear()  instance.topping_set.add(*self.cleaned_data['toppings'])  return instance