如何在Django的同一模型中获取与ForeignKey相关的主键（pk）？

Question

I need to get the id (pk) of a related model.foreignKey object in order to set the "upload_to" attr of a model.FileField of the same model.

Something like this:

class myClass(models.Model):
    related_model = models.ForeignKey(RelatedModel,on_delete=models.CASCADE)
    file = models.FileField(upload_to=str(related_model.id)+"/")

So for example, if the related_model has the primary_key 10 the upload_to attr has to be "10/"

It is possible or I have to set that value in the view.py file when the object is created?

Answer 1

Use a callable as the upload_to parameter.

def related_path(instance, filename):
    return '{}/{}'.format(instance.related_model_id, filename)

class myClass(models.Model):
    related_model = models.ForeignKey(RelatedModel,on_delete=models.CASCADE)
    file = models.FileField(upload_to=related_path)