On Dec 22, 5:20 am, eldonp2 <eldo...@gmail.com> wrote:
> Please help me understand the execution logic of a view. I have copied
> the example from the official Django documentation:
>
> def contact(request):
> if request.method == 'POST': # If the form has been submitted...
> form = ContactForm(request.POST) # A form bound to the POST
> data
> if form.is_valid(): # All validation rules pass
> # Process the data in form.cleaned_data
> # ...
> return HttpResponseRedirect('/thanks/') # Redirect after
> POST
> else:
> form = ContactForm() # An unbound form
>
> return render_to_response('contact.html', {
> 'form': form,
> })
>
> Lets imagine that I have clicked on a url that is mapped to the
> contact view. Is this the correct execution logic:
>
> 1. The else part will execute and create an unbound ContactForm
> instance that will be passed to the contact.html template
> 2. When the user clicks submit, the POST method will be executed, and
> the user will be redirected to the url '/thanks/'
>
> Please let me know if this is incorect? I'm just struggling to
> understand how the same view gets executed twice - once for the
> loading of the html page, and a second time for the POST method after
> submitting. Also, should the unbound form logic not be above the POST
> logic?
Yes, that's correct. The key is in the actual HTML - this is the
recommended way to display a form:
<form action='.' method='POST'>
So the 'action' of the form, which is the URL the data is POSTed to,
is the same as the URL used to display the form in the first place.
This is why you the same view is executed twice.
You don't need to do it this way - you could set action to a different
URL and keep the processing logic there, separate from the display
logic - but then you'd need to handle the third case when the form is
submitted, but is invalid and needs redisplaying with errors. The
pattern above handles that neatly.
--
DR.
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