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每个用户都有很多 相册，每个相册都有很多 照片。每个用户都有一组 背景图像来保存它的许多图像。类似地，用户拥有一组个人资料图片来保存其许多图像。

这些是我的模型：

class UserProfile(models.Model):
    user = models.OneToOneField(User)
    permanent_address = models.TextField()
    temporary_address = models.TextField()
    profile_pic = models.ForeignKey(ProfilePicture)
    background_pic = models.ForeignKey(BackgroundImage)


class Album(models.Model):
    user = models.ForeignKey(User)
    name = models.CharField(max_length=200)
    pub_date = models.DateTimeField(default=datetime.now)


class Photo(models.Model):
    album = models.ForeignKey(Album, default=3)
    image = models.ImageField(upload_to=get_upload_file_name)
    caption = models.CharField(max_length=200)
    pub_date = models.DateTimeField(default=datetime.now)


class BackgroundImage(models.Model):
    user = models.ForeignKey(User)
    image = models.ImageField(upload_to=get_upload_file_name)
    caption = models.CharField(max_length=200)
    pub_date = models.DateTimeField(default=datetime.now)


class ProfilePicture(models.Model):
    user = models.ForeignKey(User)
    image = models.ImageField(upload_to=get_upload_file_name)
    caption = models.CharField(max_length=200)
    pub_date = models.DateTimeField(default=datetime.now)

例如：我尝试这样做：让用户将一张 图像从ProfilePicture复制到Background Image，但没​​有奏效：

# Get the user
>>>m = User.objects.get(username='m')

# Get its set of Profile pictures
>>>m_pro_set = m.profilepicture_set.all()
>>>m_pro_set
[<ProfilePicture: pro_mik>]

# Get its set of Background images
>>>m_back_set = m.backgroundimage_set.all()
>>>m_back_set
[<BackgroundImage: bg_mik>]

# Get an image object from Profile picture of the user
>>>m_pro_1 = m.profilepicture_set.get(id=2)
>>>m_pro_1
<ProfilePicture: pro_mik>

# Get an image object from Background image of the user
>>>m_back_1 = m.backgroundimage_set.get(id=2)
>>>m_back_1
<BackgroundImage: bg_mik>

# So, I tried to copy one image from BackgroundImage of a user to ProfilePicture

>>>m_pro_set.objects.create(m_back_1)

    File "<console>", line 1, object has attribute 'objects'
AttributeError: 'QuerySet' object has no attribute 'objects'

所以我的问题是，如何将对象从一个模型复制到另一个模型？任何建议将不胜感激。

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1 回答 1

4

您需要将一个对象的属性复制到另一个对象。 create当您要创建新实例时使用，而不是要更新特定实例时使用。

m_pro = m_pro_set[0] # m_pro_set is a list and need to get the specific instance
m_pro.image = m_back_1.image
m_pro.caption = m_back_1.caption
m_pro.pub_date = m_back_1.pub_date
m_pro.save()

ProfilePicture或者，如果这是包含此功能的常见操作，您可以创建一个方法。

class ProfilePicture(models.Model):
    user = models.ForeignKey(User)
    image = models.ImageField(upload_to=get_upload_file_name)
    caption = models.CharField(max_length=200)
    pub_date = models.DateTimeField(default=datetime.now)

    def update(self, bg_img):
        self.image = bg_img.image
        self.caption = bg_img.caption
        self.pub_date = bg_img.pub_date
        self.save()

m_pro_1.update(m_back_1)因此，如果我们想要使其m_pro_1具有相同的属性，您只需要调用m_back_1

另外，如果您想创建一个新实例，我建议使用classmethod如下

class ProfilePicture(models.Model):
    ...

    @classmethod
    def create_from_bg(cls, bg_img):
        img = cls(user=bg_img.user, image=bg_img.image, caption=bg_img.caption, pub_date=bg_img.pub_date)
        img.save()
        return img

    @classmethod
    def create_from_photo(cls, photo):
        img = cls(user=photo.album.user, image=photo.image, caption=photo.caption, pub_date=photo.pub_date)
        img.save()
        return img

这会创建一个新ProfilePicture的并被使用：profile_pic = ProfilePicture.create_from_bg(m_back_1)

于 2013-11-05T19:54:09.243 回答