step03-tables.md

Step 3: Tables

You're probably familiar with object lists in NetBox. This is how we display all the instances of a certain type of object, such as sites or devices, in the user interface. These lists are generated by table classes defined for each model, utilizing the django-tables2 library.

While it would be feasible to generate raw HTML for <table> elements directly within the template, this would be cumbersome and difficult to maintain. Additionally, these dynamic table classes provide convenient functionality like sorting and pagination.

🟦 Note: If you skipped the previous step, run git checkout step02-models.

Create the Tables

We'll create two tables, one for each of our models. Begin by creating tables.py in the netbox_access_lists/ directory.

$ cd netbox_access_lists/
$ edit tables.py

At the top of this file, import the django-tables2 library. This will provide the column classes for fields we wish to customize. We'll also import NetBox's NetBoxTable class, which will serve as the base class for our tables, and ChoiceFieldColumn. Finally we import our plugin's models from models.py.

import django_tables2 as tables

from netbox.tables import NetBoxTable, ChoiceFieldColumn
from .models import AccessList, AccessListRule

AccessListTable

Create a class named AccessListTable as a subclass of NetBoxTable. Within this class, create a child Meta class inheriting from NetBoxTable.Meta; this will define the table's model, fields, and default columns.

class AccessListTable(NetBoxTable):

    class Meta(NetBoxTable.Meta):
        model = AccessList
        fields = ('pk', 'id', 'name', 'default_action', 'comments', 'actions')
        default_columns = ('name', 'default_action')

The model attribute tells django-tables2 which model to use when building the table, and the fields attribute dictates which model fields get added to the table. default_columns controls which of the available columns are displayed by default.

The pk and actions columns render the checkbox selectors and dropdown menus, respectively, for each table row; these are provided by the NetBoxTable class. The id column will display the object's numeric primary key, which is included on almost every table in NetBox but generally disabled by default. The other three columns derive from the fields we defined on the AccessList model.

What we have so far is sufficient to render a table, but we can make some small improvements. First, let's make the name column a link to each object. To do this, we'll override the default column by defining name on the class and passing linkify=True.

class AccessListTable(NetBoxTable):
    name = tables.Column(
        linkify=True
    )

Also, recall that the default_action field on the AccessList model is a choice field, with a color assigned to each choice. To display these values, we'll use NetBox's ChoiceFieldColumn class.

    default_action = ChoiceFieldColumn()

It would also be nice to include a count showing the number of rules each access list has assigned to it. We can add a custom column named rule_count to show this. (The data for this column will be annotated by the view; more on this in step five.) We'll also need to add this column to our fields and (optionally) default_columns under the Meta subclass. Our finished table should look like this:

class AccessListTable(NetBoxTable):
    name = tables.Column(
        linkify=True
    )
    default_action = ChoiceFieldColumn()
    rule_count = tables.Column()

    class Meta(NetBoxTable.Meta):
        model = AccessList
        fields = ('pk', 'id', 'name', 'rule_count', 'default_action', 'comments', 'actions')
        default_columns = ('name', 'rule_count', 'default_action')

AccessListRuleTable

We'll also create a table for our AccessListRule model using the same approach as above. Start by linkifying the access_list and index columns. The former will link to the parent access list, and the latter will link to the individual rule. We also want to declare protocol and action as ChoiceFieldColumn instances.

class AccessListRuleTable(NetBoxTable):
    access_list = tables.Column(
        linkify=True
    )
    index = tables.Column(
        linkify=True
    )
    protocol = ChoiceFieldColumn()
    action = ChoiceFieldColumn()

    class Meta(NetBoxTable.Meta):
        model = AccessListRule
        fields = (
            'pk', 'id', 'access_list', 'index', 'source_prefix', 'source_ports', 'destination_prefix',
            'destination_ports', 'protocol', 'action', 'description', 'actions',
        )
        default_columns = (
            'access_list', 'index', 'source_prefix', 'source_ports', 'destination_prefix',
            'destination_ports', 'protocol', 'action', 'actions',
        )

This should be all we need to list these objects in the UI. Next, we'll define some forms to enable creating and modifying objects.

⬅️ Step 2: Models | Step 4: Forms ➡️