django: How to get model class from model name
How do you get the model class object from a string containing model name?
This came up multiple times during SeenReport development. While recording views, saving votes and adding comment on an object, I had to get the model class using the model name. The scenario would be,
- The view receives the model name and object id
- Fetch the object from db
- Perform action on the object
However, I couldn’t find a suitable way to get model class from the model name. The best way I could find was by using the globals function. Here is how it worked,
def my_view(request, model_name, object_id): model_class = globals()[model_name] obj = get_object_or_404(model_class, id=object_id) # perform required actions and return response
However, using globals requires that the models should already be imported. This would fail for a model that didn’t exist in global scope. Also I had to needlessly import models in views.
My guess was that there should be solution in the content types framework. After poking around for a while I found ContentType.model_class. This is how the above code would look like,
def my_view(request, model_name, object_id): model_class = ContentType.objects.get(model=model_name).model_class() obj = get_object_or_404(model_class, id=object_id) # perform required actions and return response
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Pretty cool. I love the content types framework, it has saved me time in the past.
If you’re using the Django ContentTypes you’ll be getting a database hit during each model name resolution.
It would be better to use Django API for the task:
{{{
from django.db.models import get_model
# app_name should contain the model’s application name in lower case
# Example: app_name = “myfirstapp”
# Note: model name is case-insensitive
model = get_model(app_name, “MyCoolModel”)
}}}
Evgeny,
You are quite right and the suggested fix will definitely solve this performance issue…thanks