import_model_operation.py

operation.py

class ImportForeignModel(Operation):
    """Import a model from a foreign app to this one."""

    def __init__(self, app_label, model_name):
        self.app_label = app_label
        self.model_name = model_name.lower()

    def state_forwards(self, app_label, state):
        imported_model_state = state.models[self.app_label, self.model_name].clone()
        # Change the app label.
        imported_model_state.app_label = app_label
        # Default to pointing the db_table to the old one.
        default_db_table = '{}_{}'.format(self.app_label, self.model_name.lower())
        imported_model_state.options.setdefault('db_table', default_db_table)
        # Assign the new model state
        state.add_model(imported_model_state)
        # Repoint all fields referencing the old model to the new one.
        old_remote_model = '{}.{}'.format(self.app_label, self.model_name)
        new_remote_model = '{}.{}'.format(app_label, self.model_name)
        changed_models = []
        for model_key, model_state in state.models.items():
            model_changed = False
            for index, (name, field) in enumerate(model_state.fields):
                changed_field = None
                remote_field = field.remote_field
                if remote_field is None:
                    continue
                if remote_field.to.lower() == old_remote_model:
                    changed_field = field.clone()
                    changed_field.remote_field.model = new_remote_model
                through_model = getattr(remote_field, 'through', None)
                if through_model and through_model.lower() == old_remote_model:
                    if changed_field is None:
                        changed_field = field.clone()
                    changed_field.remote_field.through = new_remote_model
                if changed_field:
                    model_state.fields[index] = name, changed_field
                    model_changed = True
            if model_changed:
                changed_models.append(model_key)
        # Reload and remove the old models.
        state.reload_models(changed_models)
        state.remove_model(self.app_label, self.model_name)

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        pass

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        pass