django - Adding inline formsets without javascript

Question

I am using this post as a reference: Django: Adding inline formset rows without javascript

if request.method=='POST':
  PrimaryFunctionFormSet = inlineformset_factory(Position,Function)
  if 'add' in request.POST:
    cp = request.POST.copy()
    cp['prim-TOTAL_FORMS'] = int(cp['prim-TOTAL_FORMS'])+ 1
    prims = PrimaryFunctionFormSet(cp,prefix='prim')

I am trying to add inlines rows without javascript and came across a few things I didn't understand in the implementation referenced above.

1. How do you get a button called 'add' in your form or view or template?
2. 'prims' was defined in the form but 'prim-TOTAL_FORMS' was not. Do you need to define 'prim-TOTAL_FORMS' somewhere?
3. How can you call 'prim-TOTAL_FORMS' before you defined 'prim'?
4. Is this all writtein in the views.py?

Thanks for the help, and sorry if the questions are novice!

Answer 1

a) Add in a button with a name and value you wish, and it will be submitted as POST data, with the key in the POST being the name, and the value the value.

<input type="submit" value="true" name="add">

Read up on HTTPRequest objects in Django here.

b) No. The example uses an inlineformset_factory. This sets the TOTAL_FORMS value for you on POSTing, using the given prefix 'prim'. They are taking a copy of the current TOTAL_FORMS count, and adding 1, then returning a new formset.

c) prim is defined in the initial formset, and you are ensuring you are returning a new one with the same prefix. This code is if the form is submitted, so you know 'prim' has been set to the prefix.

d) Yes!