id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
28620	Loop on boundfields at init of inline sub-forms breaks the form set	Jonathan Rossel	DmitriySelischev	"When doing a loop (even a dummy one) on their boundfields at the init phase, the sub-forms of an inline form set are ""broken"", i.e. **the parent key field is rendered instead of being hidden and many additional SQL requests are generated**.

In this illustration case, I have 2 related models - Fig and Line - where each Fig can have many Line(s).

**forms.py**
{{{
class FigForm( ModelForm ):
    class Meta:
        model = Fig
        fields = '__all__'

class LineForm( ModelForm ):
    class Meta:
        model = Line
        fields = '__all__'
    
    def __init__(self, *args, **kwargs):
        super( LineForm, self ).__init__(*args, **kwargs)
    
        for bf in self:   # <- this screws everything
            pass          #    even with a dummy loop
    
LineFormSet = inlineformset_factory( Fig, Line, form=LineForm, extra=1 ) 
}}}

In real life, I use this loop in a custom model form class to add default CSS classes to the form widgets, but the additionnal SQL requests kill my server.


----

== Additional information

**model.py**
{{{
class Fig(models.Model):
    name = models.CharField(max_length=200,unique=True)
    xlabel = models.CharField(max_length=200,blank=True)
    ylabel = models.CharField(max_length=200,blank=True)
    descr = models.TextField(blank=True)
    pub_date = models.DateTimeField('date published',auto_now=True)
    
    def __str__(self):
        return self.name
        
    def get_absolute_url(self):
        return reverse('webplot:detail', kwargs={'pk':self.pk} )
        
    
class Line(models.Model):
    fig = models.ForeignKey(Fig, on_delete=models.CASCADE)
    x = models.CharField(max_length=200)
    y = models.CharField(max_length=200)
    label = models.CharField(max_length=20)
    
    def __str__(self):
        return self.label + ': y(x)=' + self.y + ' for x=' + self.x
        
}}}

**views.py**
{{{
def detail(request,pk='new'):
    # Used for both CREATE and UPDATE
    # create a form instance and populate it with data from the request if any
    if pk == 'new':
        fig = Fig() # instanciate empty object
    else:
        fig = get_object_or_404( Fig, pk=pk )
    
    form = FigForm( request.POST or None, instance=fig )
    subform = LineFormSet( request.POST or None, instance=fig )
    
    if request.method == 'POST':
        if form.is_valid() and subform.is_valid():
            form.save()
            subform.save()
            return redirect(fig)
    
    ctx = {'form': form, 'subform': subform }
       
    return render(request, 'webplot/detail.html', ctx )
}}}

**detail.html**
{{{
      <form method=""post"" class=""w3-container"">{% csrf_token %}
            
            <h4>Figure settings</h4>
            <table class=""w3-table"">
                {{ form.as_table }}
            </table>
            
            <h4>Line settings</h4>
            {{ subform.management_form }}
            {{ subform.non_field_errors }}
            <table class=""w3-table"">
                {% for thisform in subform.forms %}
                    {% if forloop.first %}
                        <thead>
                        <tr class=""w3-border-bottom"">
                        {% for field in thisform.visible_fields %}
                            <th>{{ field.label_tag }}</th>
                        {% endfor %}
                        </tr>
                        </thead>
                        <tbody>
                    {% endif %}
                    <tr>
                        {{ thisform.non_field_errors }}
                        {% for field in thisform.hidden_fields %}
                            {{ field }}
                        {% endfor %}
                        {% for field in thisform.visible_fields %}
                            <td>{{ field.errors }}{{ field }}</td>
                        {% endfor %}
                    </tr>
                {% endfor %}
                </tbody>
            </table>
            <input type=""submit"" value=""Submit"" class=""w3-btn"" />
        </form>
}}}
"	Bug	closed	Forms	dev	Normal	invalid	inlineformset		Unreviewed	0	0	0	0	0	0