在多对多 Django 中组合、过滤模型/视图

Question

我正在开发一个漫画书数据库，其中包含主要封面和变体封面。我有一个显示所有主要封面的页面，但我也想按出版日期的顺序组合变体封面。这是我的模型的一部分：

class Image(models.Model):
    CATEGORY_CHOICES = (
    ('Cover', 'Cover'),    
    ('Scan', 'Scan'),
    ('Other', 'Other'),
    )
    title = models.CharField(max_length=128)
    number = models.CharField(max_length=20, help_text="Do not include the '#'.")
    image = models.ImageField(upload_to="images/")
    category = models.CharField(max_length=10, choices=CATEGORY_CHOICES)
    ### The variant cover is determined by the category_choice 'Cover'. ###
    contributor = models.ManyToManyField(Contributor, blank=True, null=True)
    date_added = models.DateField(auto_now_add=True, auto_now=True)    
    def __unicode__(self):
        return self.title        
    class Meta:
        ordering = ['title']

class Issue(models.Model):
    CATEGORY_CHOICES = (
    ('Major', 'Major'),    
    ('Minor', 'Minor'),
    ('Cameo', 'Cameo'),
    ('Other', 'Other'),
    )
    title = models.ForeignKey(Title)
    number = models.CharField(max_length=20, help_text="Do not include the '#'.")
    pub_date = models.DateField(blank=True, null=True)
    cover_image = models.ImageField(upload_to="covers/", blank=True, null=True)
    ### This would be where the main image goes. ^^^ ###
    images = models.ManyToManyField(Image, related_name="images_inc", blank=True, null=True)
    ### This is where the variant covers go.^^^  ### 
    has_emma = models.BooleanField(help_text="Check if Emma appears on the cover.")

主封面页面的views.py如下所示：

def covers(request):
    sort_by = request.GET.get('sort', 'pub_date')
    if sort_by not in ['-date_added', 'date_added', '-pub_date', 'pub_date']:
        sort_by = '-date_added'
    issues = Issue.objects.filter(has_emma=True).order_by(sort_by).select_related(depth=1)
    return render_to_response('comics/covers.html', {'issues': issues}, context_instance=RequestContext(request))

但我也想显示变体封面，而不仅仅是cover_image。有没有办法做到这一点？也许有一些image 然后过滤类别（Image 模型的封面）？

我当然可以这样做：

def variants(request):
    Issue.objects.filter(has_emma=True).order_by(sort_by).select_related(depth=1)
    images = Image.objects.filter(category='Cover').order_by('id')
    return render_to_response('comics/variants.html', {'images': images}, context_instance=RequestContext(request))

但这并没有像def covers 那样给我足够的灵活性，我希望它们按pub_date 组合和排序，例如def covers。

编辑

models.py：

class Image(models.Model):
    CATEGORY_CHOICES = (
    ('Cover', 'Cover'),    
    ('Scan', 'Scan'),
    ('Other', 'Other'),
    )
    title = models.CharField(max_length=128)
    image = models.ImageField(upload_to="images/")
    category = models.CharField(max_length=10, choices=CATEGORY_CHOICES)
    date_added = models.DateField(auto_now_add=True, auto_now=True)    
    def __unicode__(self):
        return self.title        
    class Meta:
        ordering = ['title']


class Issue(models.Model):
    title = models.ForeignKey(Title)
    number = models.CharField(max_length=20)
    ######
    has_emma = models.BooleanField(help_text="Check if cover appearance.")    
    cover_image = models.ImageField(upload_to="covers/", blank=True, null=True)
    images = models.ManyToManyField(Image, related_name="images_inc", blank=True, null=True)
    ######
    def get_images(self):
        ''' Returns a list of all cover images combined,
            "main" cover image first.
        '''
        images = [self.cover_image]
        for image in self.images.filter(category='Cover'):
            images.append(image.image)
        return images   

views.py：

def covers(request):
    sort_by = request.GET.get('sort', '-pub_date')
    if sort_by not in ['-date_added', 'date_added', '-pub_date', 'pub_date']:
        sort_by = '-date_added'         
    issues = Issue.objects.filter(has_emma=True).order_by(sort_by)
    return render_to_response('template.html', {'issues': issues,}, context_instance=RequestContext(request))

模板.html： {% for issue in issues %}{% for image in issue.get_images %}{{ image.image }}{% endfor %}{% endfor %} - 不显示任何内容，但是，{% for issue in issues %} {% for image in issue.get_images %} {{ issue.cover_image }} {% endfor %} {% endfor %} 将重复显示Issue 模型的cover_image，如果有分类在Image 模型中的变体封面。

我可以做些什么来解决这个问题，以便正确显示所有内容？再次记录一下，我希望它显示{{ cover_image }}（来自Issue 模型）和{{ image.image }} 组合定义的Image 模型。

Answer 1

如果我正确理解您的问题，解决它的一种方法是向Issue 类添加一个方法，如下所示：

class Issue(models.Model):
    # fields...

    def get_images(self):
        ''' Returns a list of all cover images combined,
            "main" cover image first.
        '''
        images = [self.cover_image]
        for image in self.images.filter(category='Cover'):
            images.append(image.image)
        return images

然后，在您的模板中，您可以执行例如{% for image in issue.get_images %}...。

（如果它不是您所需要的——那么，我认为，如果您提供一些模板代码作为您想要实现的目标的示例会更好。）