CODEWITHSUNDEEP
pythondjangodjango-models
cookiedough
cookiedough

Reputation: 3840

Django: dynamic models disappear after creation

Let's say I have 2 models. Model_A and Model_B.

Whenever the admin user makes a change to an object of model_A, they click the "save" button.

So, when a "save" happens, I would like to send a post_save signal that creates a model that inherits from Model_B.

When I do so like the following, the models do get created but they disappear after refreshing the page, and sometimes they appear again after refreshing again. But they don't always stay on the list. (Weird, I know!)

So the code for the post_save signal is like so:

post_save.connect(create_new_model, sender=Model_A)

My create_new_model is like so:

def create_new_model(sender, instance, **kwargs):
    attrs = {
        'field1': models.CharField(max_length=40),
        'field2': models.CharField(max_length=40),
        '__module__': 'appname.models'
    }

    from appname.models import create_model, admin_options, modelsList

    mod = create_model(name=str(len(modelsList)),
                       fields=attrs,
                       admin_opts=admin_options
                       )
    modelsList.append(mod)

And finally, the function that creates the dynamic models (create_model) is like so:

def create_model(name, fields=None, admin_opts=None):

    from appname.models import Model_A

    attrs = fields

    model = type(name, (Model_A,), attrs)

    if admin_opts is not None:
        admin.site.register(model, admin_opts)

    return model

Does anyone know why this sneaky thing might be happening?

Upvotes: 0

Views: 104

Answers (1)

Daniel Roseman
Daniel Roseman

Reputation: 599638

This is presumably happening because your server is using more than one process. Any dynamic class will only exist within the process that creates it; and even then it won't persist across process restarts.

I don't know what your use case is here but this is certainly not the way to do it.

Upvotes: 3

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