manyToMany multipleChoiceField - how to add "checked" status

Using Django
1

hello, Im trying to setup a monitoring app, which has HostGroups and Hosts

its a ManyToMany relationships, ie

“Prod” hostgroup can include host1, host2, host3
“Webserver” hostgroup can include host1, host4, host5

so each host can be part of many Groups, and each Group can have many Hosts.

I setup my Model like this,


class Host(models.Model):
    monit_id = models.UUIDField(primary_key=True, editable=False)
    name = models.CharField(max_length=50, blank=True, null=True)

    def __unicode__(self):
        return self.name

    class Meta:
        constraints = [models.UniqueConstraint(fields=["monit_id"], name="unique_monit_id")]


class HostGroup(models.Model):
    name = models.CharField(max_length=50, blank=False, null=False)
    description = models.CharField(max_length=100, blank=True, null=True)
    host = models.ManyToManyField(Host, blank=True)

    def __unicode__(self):
        return self.name

    class Meta:
        constraints = [models.UniqueConstraint(fields=["name"], name="unique_hostgroup_name")]

my Form is appending Host choices by doing a query on the Host object

class HostGroupForm(forms.ModelForm):
    class Meta:
        model = HostGroup
        fields = "__all__"

    name = forms.CharField(max_length=40, required=True)
    description = forms.CharField(max_length=50, required=False)
    host = forms.MultipleChoiceField(required=False, widget=forms.CheckboxSelectMultiple)

    def __init__(self, *args, **kwargs):
        super(HostGroupForm, self).__init__(*args, **kwargs)
        self.fields['host'].choices = [(host.monit_id, host.name) for host in Host.objects.filter(approved=True)]

and finally my view saves the incoming form and creates a ManyToMany relationship in the M2M table that gets created automatically

if request.method == "POST":
        obj = HostGroup.objects.get(pk=id)
        form = HostGroupForm(request.POST, instance=obj)
        if form.is_valid():
            obj = form.save(commit=True)
            for h in request.POST.getlist('host'):
                obj.host.add(h)

I can see the relationship created from the obj.host.add(h) line

ksnip_20240723-182806
ksnip_20240723-1828061219×691 66.5 KB

what I cant figure out is how to display the selected Hosts in the Group when the form is presented back to the template, right now it displays a blank list of all hosts from the query in the Form class,

how can i make it automatically “check” a checkbox if the host is in a Many2Many relationship with a HostGroup ?

ksnip_20240723-183106
ksnip_20240723-1831061376×842 41.3 KB

Idea is to show the user all possible hosts that he can add to the HostGroup, and show which hosts are already part of this HostGroup (with a checkmark)

thanks

2

maybe it help…

3

To ensure that the checkboxes are automatically checked for hosts that are already part of the HostGroup when the form is presented back to the template, you need to set the initial values for the host field in the form. This can be done in the __init__ method of your HostGroupForm.

Here is the updated code for your form:

    class Meta:
        model = HostGroup
        fields = "__all__"

    name = forms.CharField(max_length=40, required=True)
    description = forms.CharField(max_length=50, required=False)
    host = forms.MultipleChoiceField(required=False, widget=forms.CheckboxSelectMultiple)

    def __init__(self, *args, **kwargs):
        super(HostGroupForm, self).__init__(*args, **kwargs)
        self.fields['host'].choices = [(host.monit_id, host.name) for host in Host.objects.filter(approved=True)]
        
        # If an instance is provided, set the initial values for the host field
        if 'instance' in kwargs:
            self.fields['host'].initial = [host.monit_id for host in kwargs['instance'].host.all()]

In your view, make sure to pass the instance of HostGroup to the form when you are editing an existing group:

if request.method == "POST":
    obj = HostGroup.objects.get(pk=id)
    form = HostGroupForm(request.POST, instance=obj)
    if form.is_valid():
        obj = form.save(commit=True)
        obj.host.set(request.POST.getlist('host'))
else:
    obj = HostGroup.objects.get(pk=id)
    form = HostGroupForm(instance=obj)

return render(request, 'your_template.html', {'form': form})