如何在Django的ImageField的路径中设置变量？

Question

This is my models.py :

class Group_Photo(models.Model):

    group_id = models.ForeignKey(Group)
    photo = models.ImageField(upload_to="static/image/group/" + group_id + "/")

I'd like to upload images to a directory which is for a group. For example, if the group_id = 3 ,

upload_to="static/image/group/3/"

How should I do?

Sorry, this is the error.

File "/models.py", line 161, in Group_Photo photo = models.ImageField(upload_to="static/image/group/" + group_id + "/") TypeError: Can't convert 'ForeignKey' object to str implicitly

Answer 1

The upload_to argument can be a function, as described in the documentation :

def group_based_upload_to(instance, filename):
    return "image/group/{}/{}".format(instance.group.id, filename)

class Group_Photo(models.Model):
    group = models.ForeignKey(Group)
    photo = models.ImageField(upload_to=group_based_upload_to)

The function takes two arguments - instance of the model to which the file is being attached and the original name of the file. It has to return a relative path under witch the file will be saved. It will be appended to the path defined in the MEDIA_ROOT setting.

The example above uses directories based on group's numeric id. You can obviously use other fields, for example to use the slug (if it has one) just replace instance.group.id with instance.group.slug .