Django: How to implement system flags

Question

I am developing an application in Django and I am curious on how I can go about adding a model such that only 1 row is only ever present (i.e. Singleton).

As an example, I'd like to maintain a set of boolean flags of the application i'm running as to whether: it's on or off (so I can manually turn it on or off, perhaps even per module).

I can't see any part of the docs explaining a good way to go about setting this up.

Any suggestions?

We have no clue what any of this is for. – Ignacio Vazquez-Abrams Oct 05 '11 at 17:56 — Ignacio Vazquez-Abrams, Oct 05 '11 at 17:56
re-explained to help clarify hopefully – Setheron Oct 05 '11 at 18:10 — Setheron, Oct 05 '11 at 18:10
I don't think that's what singleton means. – Jorge Orpinel Pérez Nov 22 '17 at 04:51 — Jorge Orpinel Pérez, Nov 22 '17 at 04:51

score 1 · Accepted Answer · answered Oct 05 '11 at 18:46

Not sure from you explanation in what context you require this but I have a model which holds a number of key/value pairs used in validator checks and other things. The keys are all needed by each implementation of the project but the values will differ between projects. The values should be maintainable by an admin user. The values usually do not need to change very much once set. Given that, I decided to put them in a model. It is a bit weird but simple enough.

You should be able to limit write access to the model to the one row for either your app or your users through your code.
only ever reference the first row in the QuerySet
```
row = MyVariables.objects.all()[0]
```

Test if there are rows first. if you think there might accidentally be more than one record then make sure it is ordered (but that should never happen if you did (1) correctly.

score 1 · Answer 2 · answered Oct 05 '11 at 21:24

1

There are a couple of apps already dealing with this, check out http://djangopackages.com/grids/g/live-setting/

answered Oct 05 '11 at 21:24

Danny W. Adair

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score 0 · Answer 3 · edited May 23 '17 at 12:19

I'm also a bit confused on your goal, but I'd recommend looking at the Model Instance section of the docs. You should probably look at customizing the validation or cleaning of the model.

If your goal is to only have 1 row flagged in the table for your model: during the validation you can run a query to see if any other row is flagged, and update them to be not flagged. (or delete them).

This question Unique BooleanField value in Django may be helpful.

Django: How to implement system flags

3 Answers3