Django custom manager - how to use custom manager before QuerySet

Question

I am building my own custom manager to get translations of a model. The Idea is:

main model:

class BlogTranslationManager(models.Manager):        
    def language(self):
        lang = translation.get_language()
        return BlogTranslation.objects.filter(lang=lang)

class ArticleTranslationManager(models.Manager):
    def language(self):
        lang = translation.get_language()
        return ArticleTranslation.objects.filter(lang=lang)

class Blog(models.Model):
    created = models.DateTimeField()
    objects = models.Manager()
    translations = BlogTranslationManager()

    # PROBLEM HERE
    @property
    def articles(self):
        # here I need translations of all articles of this blog
        # I cannot do: 
        return self.blog_articles.translations.language('en')
        # because 'translations' Manager cannot be called on QuerySet
        # what can I do here? am I missing something in CustomManagers? 


class Article(models.Model):
    blog = models.ForeignKey(Blog, related_name="blog_articles")
    objects = models.Manager()
    translations = ArticleTranslationManager()

class BlogTranslation(models.Model):
    book = models.ForeignKey(Book, related_name="book_translations")
    field_name = models.CharField(max_length=10)
    lang = models.CharField(max_length=3)
    translation = models.TextField()

class ArticleTranslation(models.Model):
    article = models.ForeignKey(Article, related_name="article_translations")
    field_name = models.CharField(max_length=10)
    lang = models.CharField(max_length=3)
    translation = models.TextField()

and in template, I want to able to call:

{{ blog.articles }}

I described the problem right inside the code above, any ideas about it? any help is highly appreciated!

Answer 1

Try using the Article.translations manager first, then filter the resulting queryset. If I understand your models correctly, you want something like:

@property
def articles(self):
    return Article.translations.language('en').filter(article__blog=self)