Default value for category field

[Century1026]

Hello,

As you can see, name field can display the first item on category list with default value, but when I add default: PartCategory.objects.first() to category field, the form isn't even opening.

How can I add a default value for category field?
Looking forward to your answer!

partial code in part.js

function partFields(options={}) {

    var fields = {
        category: {
            filters: {
                structural: false,
            },
            tree_picker: {
                url: '{% url "api-part-category-tree" %}',
                default_icon: global_settings.PART_CATEGORY_DEFAULT_ICON,
            },
        },
        name: {
            default: PartCategory.objects.first().name,
        },
    if (options.category) {
        fields.category.value = options.category;
    }
    return fields;
}

[SchrodingersGat]

You cannot use PartCategory.objects.first().name in front-end javascript code. This is a database call, made by python / django in the backend.

[Century1026]

Hi, Oliver
Thank you for your prompt answer!
I'm sorry I get it wrong, PartCategory.objects.first().name works here in models.py.

    name = models.CharField(
        max_length=100, 
        blank=False, 
        default=PartCategory.objects.first().name,
        help_text=_('Part name'), 
        verbose_name=_('Name')
    )

But why adding default=PartCategory.objects.first() is not working for category? Does it require id or pk number? If so, how can I fetch it?
models.py

category = TreeForeignKey(
    PartCategory,
    related_name='parts',
    null=True,
    blank=True,
    on_delete=models.DO_NOTHING,
    default=PartCategory.objects.first(),#nothing happened?
    verbose_name=_('Category'),
    help_text=_('Part category'),
)

[Century1026]

A little bit of context here...

I noticed that user can intitialize stock quantity and location when creating part. It's efficient as additional steps to edit stock are saved. As expiry date is also a primary prop, I added "Initial Stock Expiry Date" field to "Create Part" form and it worked perfectly(see attached video).
https://github.com/inventree/InvenTree/assets/106154819/1c2d4cc6-29d7-419b-a68c-9ab3d6d84186

To further improve efficiency, I wanna realize that when "initial location" is selected, the name field instantly generate a ref number like A-a-1, with each character represents locations and sublocations.

Therefore, to save time creating testing parts, I hope fields can be auto-filled. Unnecessary fields are hid and initial stock quantity field is able to generate a random number (that's why I was making changes in part.js). Currently I only have category field un-auto-filled.

[SchrodingersGat]

Default field values cannot be specified "dynamically" like that - you should read more about how field defaults work

The "default" value gets evaluated only once, when the code first runs - and not every time you instantiate a field.

The way to do it dynamically is to inject a new default value into the form on the frontend. The new (React) interface has a much more comprehensive and powerful framework for achieving this.

[Century1026]

Thank you for your kind guidance, I'm getting more familiar of how it works!

[Century1026]

I suddenly realize that when editing a part, the category and name field are auto-filled. Maybe I could learn the way it presents value just like how I added initial_stock_expiry_date.

In the latter part of part.js, I found this

function editPart(pk) {

    var url = `{% url "api-part-list" %}${pk}/`;

    var fields = partFields({
        edit: true
    });

    // Filter supplied parts by the Part ID
    fields.default_supplier.filters.part = pk;

    var groups = partGroups({});

    constructForm(url, {
        fields: fields,
        groups: groups,
        title: '{% trans "Edit Part" %}',
        reload: true,
        successMessage: '{% trans "Part edited" %}',
    });
}

The function accepts a pk number to fetch value, I then searched for "editpart" and found this

    $("#part-edit").click(function() {

        editPart({{ part.pk }});
    });
    {% endif %}

Apparently, when you click editpart button, you are already under certain part info page. But when creating new part, no pk can be fetched.

[wolflu05]

Regarding the python (backend) and javascript (frontend) mixes, refer to the comments above. But if you want to build a system that automatically sets fields for you, I would suggest creating a custom plugin rather than running a modified version of InvenTree. There are several mixing available. I would recommend taking a look at the event mixin which you could use to set certain values on a item creation.

[Century1026]

Thank you for your answer! Will look into it.