Django update_or_create with potentially null idenitfier-CodePudding

I have a function in Django that accepts a post request. If that post request includes an id, I want to update that object. If the post request sends a blank/null id, I'd like to create a new object and have Django set the ID (primary key) of the model.

Here is what I have:

def save_user_roster_to_db():
name = request.data['name']
id = request.data['id'] # this could be null/blank or be an ID
try:
    user_roster = SavedUserRoster.objects.update_or_create(
        id=id,
        defaults={
            "name": name,
        }
    )
    return user_roster.pk
except:
    raise Exception

However, this seems to try to assign the blank/null value as the ID when creating a new object. How can I tell Django to set its own ID (which is the primary key) if it's creating a new object?

CodePudding user response：

You can't use update_or_create with the id field. Because in the current situation, id can have a value of None, and the Django model can't create the object with an id of None. So I think you can try like the following.

def save_user_roster_to_db():
    name = request.data['name']
    id = request.data['id'] # this could be null/blank or be an ID
    try:
        if id:
            user_roster = SavedUserRoster.objects.get(pk = id).update(name = name)
        else:
            user_roster = SavedUserRoster.objects.create(name = name)
        return user_roster.pk
    except:
        raise Exception

CodePudding user response：

Traditionally id is auto generated and always unique. In this case replacing None id will create exception when you create record for first time.

There are two possible options.

OPTION 1: Create another unique_identified i.e username or email.

def save_user_roster_to_db():
name = request.data['name']
unique_identified = request.data['unique_identified'] # this could be null/blank or be an ID
user_roster, is_created = SavedUserRoster.objects.update_or_create(
        unique_identified=unique_identified,
        defaults={
            "name": name,
        }
    )
return user_roster.pk

OPTION 2:

For Create: Get the last id from database and add 1 with last id, so that It will be the next id value, It will avoid the None exception.

For Update: It will update the existence record against id

def save_user_roster_to_db():
name = request.data['name']
id = request.data['id'] # this could be null/blank or be an ID
if id is None:
   id = int(MyUserModel.objects.all().last().id) 1
user_roster, is_created = SavedUserRoster.objects.update_or_create(
        id=id,
        defaults={
            "name": name,
        }
    )
return user_roster.pk