How to loop over the registered types#

The registry knows every sample and measurement type in the portal, so code that has to work for all of them can ask it instead of naming each one. You do this for a page that counts records by type, a report or a command that visits every type.

Before you start#

You need at least one registered type. See How to register a sample or measurement type.

Steps#

Import the registry.
```
from fairdm.registry import registry
```

Choose what to loop over.

To get	Use	Each item is
The sample types	`registry.samples`	A model class
The measurement types	`registry.measurements`	A model class
Both	`registry.models`	A model class
Every configuration	`registry.get_all_configs()`	A `ModelConfiguration`

Fetch the configuration of each model when you need it.

for model in registry.samples:
    config = registry.get_for_model(model)
    print(config.get_verbose_name_plural(), model.objects.count())

Use what the configuration offers. A configuration names its model as config.model, its listing as the URL name <config.get_slug()>-list and its generated components through accessors such as get_table_class(). This function returns one row for each type, with its name, its record count and the address of its listing.

from django.urls import reverse

from fairdm.registry import registry


def type_summary():
    rows = []
    for config in registry.get_all_configs():
        rows.append(
            {
                "name": config.get_verbose_name_plural(),
                "count": config.model.objects.count(),
                "url": reverse(f"{config.get_slug()}-list"),
            }
        )
    return rows

In a template, ask about one model or record with the get_registry_info tag. It returns nothing for a model that is not registered.

{% load fairdm %}
{% get_registry_info object as info %}
{% if info %}{{ info.get_verbose_name_plural }}{% endif %}

The result#

type_summary() returns a list like this when the portal has two registered types:

[
    {"name": "Plant Samples", "count": 12, "url": "/collections/samples/plantsample/"},
    {"name": "Leaf Area Measurements", "count": 40, "url": "/collections/measurements/leafareameasurement/"},
]

The lists come back in the order the types were registered, and each call builds a new list, so changing one changes nothing in the registry.

To check one model without a loop, call registry.is_registered(model), which returns False where get_for_model would raise. The registry’s methods and properties are on The registry, and the configuration’s methods are on Model configuration.