Add ability to have a per-model prefix

[PawelDecowski]

It would be nice to be able to specify a per-model prefix, eg:

class User(models.Model)
    id = AutoHashId(primary_key=True, prefix='us_')
    # ids like us_3n3b3hjbjh4

class Project(models.Mode)
    id =  AutoHashId(primary_key=True, prefix='pr_')
    # ids like pr_j5f7l3hg5k5l

[nshafer]

Not a bad idea, and you're not the only one to think of it. I just found @pegler has created a fork with that functionality. I'll review his work.

[pegler]

Cool. We've been using my fork for a few weeks developing a new API. There are two features on that fork, so if you only want prefix support, we'll need to clean it up a bit.

The other is a new proxy field thats let you, for example, have both an id and hash_id fields, where hash_id only accepts and returns hashids and is a virtual/proxy field andid still functions like before. We needed this to support legacy systems that only lookup by integer ID, while we want some new systems to only look up by hashid. HASHID_FIELD_ALLOW_INT_LOOKUP wouldn't work because it would allow the new systems to look up by hashid or int, which was not acceptable.

[nshafer]

Ahh, interesting. I'll have to take a look when I get a chance.

[bjmc]

I'd be very interested in this feature. We'd like to prefix our IDs with a tag URI scheme to produce globally-unique identifiers.

Would the maintainers be interested in accepting a PR?

[nshafer]

Added in 3.2, thanks @bjmc

[bjmc]

Hi @nshafer thanks for accepting my MR! Can I ask you to hold off on making a release for a week or so? I actually think what I've done could stand some improvement. I think it might be better if the prefix callable executed in the context of the descriptor when it's accessed, instead of at model-definition time when the field is associated with the model.

[nshafer]

OK, I have just removed the callable support for now so that it doesn't hold up a new release. I did think it was a little superfluous since it's called in pretty much the same context as just setting the string, but I figured there was a use-case I wasn't aware of or thinking of. I'll take another PR once it's more defined.