Disallow deleting a member of a form collection

[YLITC]

When using a formset factory in Django you can use the parameter can_delete to control whether to allow deleting of the formset members. Can this be done in Django-formset?
It would be nice to have the ability for each member of the collection control whether it can be deleted or not.
If this cannot be done currently in Django-formset what would be the best way for me implement this?

[jrief]

Interesting use-case.

I somehow have a problem with this from a UX perspective: A user shall have always have the possibility to undo an action which he previously executed. If by accident he clicked onto the "Add …"-button, then he wouldn't have that possibility anymore and this can lead to frustration and even panic.

[YLITC]

My use case is a Facility with Units. Every facility when created automatically gets a default unit with a 'special' name. This one should not be deleted OR changed. A User can add or delete Units - certainly the ones they add - but not the default one. Yet I do want the default one to show up in the list of units when viewing the facility.

[jrief]

I assume that you have a definition similar to this:

class UnitForm(ModelForm):
    # some fields

class UnitCollection(FormCollection):
    min_siblings = 1
    max_siblings = ...
    unit = UnitForms(…)

class FacilityForm(ModelForm):
    # some fields

class FacilityCollection(FormCollection):
    facility = FacilityForm()
    units = UnitCollections()

How about refactoring the FacilityCollection into:

class FacilityCollection(FormCollection):
    facility = FacilityForm()
    default_unit = UnitForm()
    units = UnitCollections()

you then achieve what you want, without having to change the core implementation of django-formset.

[YLITC]

good approximation of what I have 👍
I was thinking something along that line. Let me try it. But what about ordering ...

[jrief]

Well, ordering than only works for the non-default UnitForm. If that faeture is required as well, then yes, I would need to add an extra flag can_delete to each form. However, I'm somehow reluctant on this.

[YLITC]

What is the reluctance? if I may ask

[jrief]

not very convinced (yet) that this is the right approach.

[YLITC]

I just can't get it work!
I have something like:

class UnitCollection(FormCollection):
    min_siblings = 1
    max_siblings = ...
    legend = "Units"
    unit = UnitForms(…)

class FacilityCollection(FormCollection):
    facility = FacilityForm()
    default_unit = UnitForm()
    units = UnitCollections()

Problem is that the default_unit keeps getting the data from the parent instance; the Facility. I have tried setting the instance which didn't work. Will using model_to_dict work - though I am not sure how it will work - can you help me?
Regardless seems like more code and complication then having a can delete option!
Also the legend (in UnitCollection) will only be on the units and will not include the default unit.

[jrief]

Please add your forms/collections to /testapp and point me onto your fork of the project. I then will have a look at it.