Use object instance when getting _meta info in admin

[frennkie]

Make sure to use the object instance in admin.py in order to get the correct app_label and model_name. This is important when a subclass (e.g. of Newsletter) is used.

fix #330

[frennkie]

Changed to Draft as tests are failing (worked on my machine).. will look into it.

[coveralls]

Coverage remained the same at 88.389% when pulling 6a25089 on frennkie:fix-app-label into 57ac58d on dokterbob:master.

[frennkie]

The tests prevented me from making a mistake. I don't think this can be "fixed". But other line is being fixed in this PR. Makes it easer to subclass.

[dokterbob]

The tests prevented me from making a mistake. I don't think this can be "fixed". But other line is being fixed in this PR. Makes it easer to subclass.

Why can't it be fixed? It seems obj is a class instance (just from looking at it), so it does seem it would have the same behaviour. Could you verify this, for completeness sake?

Thanks! Great contribs! Forgot how much fun Open Source was. 🙌

[frennkie]

Why can't it be fixed? It seems obj is a class instance (just from looking at it), so it does seem it would have the same behaviour.

Yes, obj is an model instance. It has the opts attribute. The way the other classes are passed into model appears to be different. Even it I instantiate them (run model().opts) there is no opts attribute.. :-/

Update: I think I found it.. the opts attribute is not on the Model but on the ModelAdmin and set when that is instatiated: https://github.com/django/django/blob/master/django/contrib/admin/options.py#L589

[dokterbob]

Right. Thanks for the feedback.

Are the API's used here documented API's? If not, they might be eligible to change and thus they might add additional maintenance load. In such case, perhaps it's wise to keep this work alive in a branch or a fork, until a stable API allows us to implement this well. I feel that subclassing the Newsletter model is a rather limited use case, as most people requiring such functionality have been making the modifications in their own forks of the project.

What are your thoughts about this?