Developing Configurable Component in Django
I like writing reusable code. What I like more is writing code for configurable components. For this project, I wanted to develop a component that fetches data from the database and create graphs and charts. It sounds easy, right? Well, it was. But, it felt a bit challenging to me at first.
I was okay with configurable queries, it was very straightforward to implement
it. But, making those queries on configurable models was troubling me. I kind
of got stuck on this. And then, swappable models occurred to me. In OpenWISP,
we have used the swapper module to load models. The
swapper module allows users to
replace the existing models with custom ones without any hassle. It took me a
while to wrap my head around swappable models.
The major hurdle was down and I had to just provide other properties for querying the database. I provided the configuration of the query parameters as below:
CONFIG = [
{
'app_label': 'home',
'model': 'orders',
'aggregate_by': 'zone'
}
]
The above configuration was processed by the following code to fetch data from the database.
data = {}
for entry in CONFIG:
model = load_model(entry['app_label'],entry['model'])
qs = model.objects.all().values(entry['aggregate_by']).annotate(
count=Count(entry['aggregate_by'] )
)
data[entry[model_name]] = qs
The feature I was working on was concerned about the aggregated data, hence the above code query accounts only for that. But, the query can be enhanced by using a sub dictionary in the configuration and passing it along in code as follows
CONFIG = [
{
'app_label': 'home',
'model': 'orders',
'aggregate_by': 'zone'
'query_params': {
'order_date__lte': '2020-12-30'
}
}
]
The code for querying will be modified as below:
qs = model.objects.filter(**entry['query_params']).values(entry['aggregate_by']).annotate(
count=Count(entry['aggregate_by'] )
)
I will keep looking for ways to make the database query more configurable.
In other news
Another round of triaging and reviews of PR in OpenWISP. But, today’s reviews were not as comprehensive as I like. I don’t want to step on someone else’s review cycle.