保存方法很多

发布于 2024-08-19 00:54:02 字数 1389 浏览 2 评论 0原文

我有一个名为 Card 的模型，它与标签。当我保存卡片时，我也想创建一个产品，我想要有相同的多对多关系来标记。

如何访问实例的标签？ self.tags.all() 给出一个空列表，而如果我保存后检查，该卡实际上有标签。我的代码如下。作为记录，我使用的是 Django 1.0.5。

class Card(models.Model): 
    product     = models.ForeignKey(Product, editable=False, null=True) 
    name       = models.CharField('name', max_length=50, unique=True, help_text='A short and unique name or title of the object.') 
    identifier = models.SlugField('identifier', unique=True, help_text='A unique identifier constructed from the name of the object. Only change this if you know what it does.', db_index=True) 
    tags       = models.ManyToManyField(Tag, verbose_name='tags', db_index=True) 
    price      = models.DecimalField('price', max_digits=15, decimal_places=2, db_index=True) 
    def add_product(self): 
        product = Product( 
            name = self.name, 
            identifier = self.identifier, 
            price = self.price 
        ) 
        product.save() 
        return product 
    def save(self, *args, **kwargs): 
        # Step 1: Create product 
        if not self.id: 
            self.product = self.add_product() 
        # Step 2: Create Card 
        super(Card, self).save(*args, **kwargs) 
        # Step 3: Copy cards many to many to product 
        # How do I do this? 
        print self.tags.all() # gives an empty list??

原文

I've got a model called Card which has a ManyToMany relationship to
Tag. When I save a Card, I'd like to create a Product as well, which I
want to have the same ManyToMany relationship to tag.

How do I access the instance's tags? self.tags.all() gives an empty
list, while if I check after saving, the card actually has tags. My
code is below. For the record, I am using Django 1.0.5.

class Card(models.Model): 
    product     = models.ForeignKey(Product, editable=False, null=True) 
    name       = models.CharField('name', max_length=50, unique=True, help_text='A short and unique name or title of the object.') 
    identifier = models.SlugField('identifier', unique=True, help_text='A unique identifier constructed from the name of the object. Only change this if you know what it does.', db_index=True) 
    tags       = models.ManyToManyField(Tag, verbose_name='tags', db_index=True) 
    price      = models.DecimalField('price', max_digits=15, decimal_places=2, db_index=True) 
    def add_product(self): 
        product = Product( 
            name = self.name, 
            identifier = self.identifier, 
            price = self.price 
        ) 
        product.save() 
        return product 
    def save(self, *args, **kwargs): 
        # Step 1: Create product 
        if not self.id: 
            self.product = self.add_product() 
        # Step 2: Create Card 
        super(Card, self).save(*args, **kwargs) 
        # Step 3: Copy cards many to many to product 
        # How do I do this? 
        print self.tags.all() # gives an empty list??

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

记忆之渊 2024-08-26 00:54:02

您是否使用 django-admin 来保存模型和标签？直到模型的保存后信号发出后，多对多字段才会保存在那里。在这种情况下，您可以做的是覆盖管理类 save_model 方法。例如：

class CardAdmin(admin.ModelAdmin):

    def save_model(self, request, obj, form, change):
        obj.save()
        form.save_m2m()
        #from this point on the tags are accessible
        print obj.tags.all()

Are you using the django-admin to save the model and tags? The many-to-many fields don't get saved there until after the post-save signal of the model. What you can do in this case is overide the admin classes save_model method. E.g.:

class CardAdmin(admin.ModelAdmin):

    def save_model(self, request, obj, form, change):
        obj.save()
        form.save_m2m()
        #from this point on the tags are accessible
        print obj.tags.all()

回复收藏 0 原文