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django的可恢复模型成员

dry django-models inheritance django python

Dagg Nabbit · 技术社区 · 15 年前

我有这样一个django模型:

class Something(models.Model):    
    title = models.CharField(max_length=200, default=u'')
    text  = models.CharField(max_length=250, default=u'', blank=True)
    photo = models.ImageField(upload_to=u'something')
    def photo_thumb(self):
        if self.photo:
            return u'<img src="%s" />' % (settings.MEDIA_URL + '/thumbs/?h=64&w=80&c=50x0&p=' + self.photo.name)
        else: 
            return u'(no photo)'
    photo_thumb.short_description = u'Photo'
    photo_thumb.allow_tags = True
    photo_thumb.admin_order_field = 'photo' 
    def __unicode__(self):
        return self.title;

class SomethingElse(models.Model):    
    name = models.CharField(max_length=200, default=u'')
    foo  = models.CharField(max_length=250, default=u'', blank=True)
    photo = models.ImageField(upload_to=u'something_else')
    def photo_thumb(self):
        if self.photo:
            return u'<img src="%s" />' % (settings.MEDIA_URL + '/thumbs/?h=64&w=80&c=50x0&p=' + self.photo.name)
        else: 
            return u'(no photo)'
    photo_thumb.short_description = u'Photo'
    photo_thumb.allow_tags = True
    photo_thumb.admin_order_field = 'photo' 
    def __unicode__(self):
        return self.title;

我觉得这是干的,原因很明显。我的问题是,我能把这个放在别的地方吗:

    # ...
    def photo_thumb(self):
        if self.photo:
            return u'<img src="%s" />' % (settings.MEDIA_URL + '/thumbs/?h=64&w=80&c=50x0&p=' + self.photo.name)
        else: 
            return u'(no photo)'
    photo_thumb.short_description = u'Photo'
    photo_thumb.allow_tags = True
    photo_thumb.admin_order_field = 'photo' 
    # ...

然后用一行代码将其包含在相关的模型类中?或者可以通过某种方式动态地添加到相应的类中?我尝试过经典遗传和寄生遗传,但我可能做得不对。。。我对Django和python都很陌生。感谢您的帮助。

4 回复 | 直到 15 年前

satoru 15 年前

另一种解决方案是创建 ImageField 并覆盖 contribute_to_class 方法:

class ImageWithThumbnailField(ImageField):
    def contribute_to_class(self, cls, name):
        super(ImageWithThumbnailField, self).contribute_to_class(cls, name)


        def photo_thumb(self):
            photo = getattr(self, name, None)
            if photo:
               return u'<img src="%s" />' % (settings.MEDIA_URL + '/thumbs/?h=64&w=80&c=50x0&p=' + photo.name)
            else: 
               return u'(no photo)'
        photo_thumb.short_description = u'Photo'
        photo_thumb.allow_tags = True
        photo_thumb.admin_order_field = 'photo' 

        setattr(cls, 'photo_thumb', photo_thumb);

photo_thumb 你所期待的方法的存在 self.photo

编辑 :请注意,您可以使用 getattr(self, name) 动态访问字段。所以是的,我们有一些照片现场。

Filip DupanoviÄ 15 年前

我同意金陶塔斯的说法。一般的经验法则是,如果需要重用模型字段和元选项,则创建一个抽象模型类;如果只需要重用其他属性和方法,则使用一个简单的类。

photo 模型字段):

class PhotoModels(models.Model):

    photo = models.ImageField(upload_to=u'something')

    def photo_thumb(self):
        if self.photo:
            return u'<img src="%s" />' % (settings.MEDIA_URL +
                   '/thumbs/?h=64&w=80&c=50x0&p=' + self.photo.name)
        else: 
            return u'(no photo)'

    photo_thumb.short_description = u'Photo'
    photo_thumb.allow_tags = True
    photo_thumb.admin_order_field = 'photo'

    class meta:
        abstract = True

class Something(PhotoModels):    
    title = models.CharField(max_length=200, default=u'')
    text = models.CharField(max_length=250, default=u'', blank=True)

class SomethingElse(PhotoModels):    
    name = models.CharField(max_length=200, default=u'')
    foo = models.CharField(max_length=250, default=u'', blank=True)
    photo.upload_to = u'something_else'

    def __unicode__(self):
        return self.title;

class PhotoModels:

    def photo_thumb(self):
        if self.photo:
            return u'<img src="%s" />' % (settings.MEDIA_URL +
                   '/thumbs/?h=64&w=80&c=50x0&p=' + self.photo.name)
        else: 
            return u'(no photo)'

    photo_thumb.short_description = u'Photo'
    photo_thumb.allow_tags = True
    photo_thumb.admin_order_field = 'photo' 

class Something(models.Model, PhotoModels):    
    title = models.CharField(max_length=200, default=u'')
    text = models.CharField(max_length=250, default=u'', blank=True)
    photo = models.ImageField(upload_to=u'something')

class SomethingElse(models.Model, PhotoModels):    
    name = models.CharField(max_length=200, default=u'')
    foo = models.CharField(max_length=250, default=u'', blank=True)
    photo = models.ImageField(upload_to=u'something_else')

    def __unicode__(self):
        return self.title;

Gintautas Miliauskas 15 年前

当然你可以重用代码。把它分解成一个基类,让两个类都继承这个基类。那应该很管用。只是别忘了基类需要从模型。模型本身(那么我建议 making it abstract 新的mixin基类。

Dagg Nabbit 15 年前

http://docs.djangoproject.com/en/dev/topics/db/models/#abstract-base-classes

我会检查确认的。