Django模型按外键过滤

Question

我在从一组模型中过滤对象时遇到了一些麻烦.这是问题所在:

我有3个班:

class Autor(models.Model):    
    nome = models.CharField(max_length=50)
    slug = models.SlugField(max_length=50, blank=True, unique=True)
    foto = models.ImageField(upload_to='autores/', null=True, blank=True)
    ...

class CategoriaRecolha(models.Model):
    categoria = models.CharField(max_length=30)
    descricao = models.TextField()
    slug = models.SlugField(max_length=30, blank=True, unique=True)
    ...

class Recolha(models.Model):    
    titulo = models.CharField(max_length=100)
    slug = models.SlugField(max_length=100, blank=True, unique=True)
    descricao = models.TextField()
    ficha_tec = models.TextField()
    categoria = models.ForeignKey(CategoriaRecolha)
    autor = models.ForeignKey(Autor)
    ....

我想要检索的是Autor类的字段,其中Recolha类的字段categoria等于特定值.

以一种更简单的方式,我需要获得参与特定类别的所有autor.

谢谢

Answer 1

更直接的选择:

autors = Autor.objects.filter(recolha__categoria=MyCategoria)

MyCategoria相关CategoriaRecolha实例在哪里.或者,如果要再次匹配特定的类别名称,可以将查询扩展到另一个级别:

autors = Autor.objects.filter(recolha__categoria__categoria='my_category_name')

Answer 2

在django 2中是ForeignKey.limit_choices_to docs

staff_member = models.ForeignKey(
    User,
    on_delete=models.CASCADE,
    limit_choices_to={'is_staff': True},
)

Answer 3

cat = CategoriaRecolha.objects.get(field=value)
rows = Recolha.filter(categoria=cat)
autors = [row.autor for row in rows]

在Django文档解释这相当不错。