django form dropdown list of stored models

Question

I am trying to create a form for a library where a user can perform 2 actions: add a new book or open the stored information of an existing one. Books have 2 fields (title and author). Every time a new book is created, it is stored at the database. Any previously created book is shown as an option at a dropdown list (only the name). I want that when a user selects an option from the dropdown list, the information of the selected book appears on screen.

I have been trying 2 different approaches, but none of them fulfills my requirements. On one hand, following this question django form dropdown list of numbers I am able to create a dropdown list, and get the selected value at views with some code like that:

class CronForm(forms.Form):
    days = forms.ChoiceField(choices=[(x, x) for x in range(1, 32)])

def manage_books(request):
    d = CronForm()
    if request.method == 'POST':
        day = request.POST.get('days')

But I want my options to be the previously stored books at the data base, and not pre-defined values.

An other approach I have tried is to do it from the html template. There I create the following form:

<form>
    {% for book in list %} 
        <option value="name">{{ book.name }}</option>
    {% endfor %}   
</form>

Where book is rendered at views from this:

l = Books.objects.all().order_by('name')

In this second case the information shown at the dropdown list is the one I want, but I don't know how to get the selected value and use it at views. Perhaps using a javascript function?

So my 2 requirements are: show the correct info at the list (the stored at the DB by the user) and be able to know which one has been selected.

Answer 1

You should use ModelChoiceField.

class CronForm(forms.Form):
    days = forms.ModelChoiceField(queryset=Books.objects.all().order_by('name'))

Then your views, it should look something like this:

def show_book(request):
   form = CronForm()
   if request.method == "POST":
      form = CronForm(request.POST)
      if form.is_valid:
         #redirect to the url where you'll process the input
         return HttpResponseRedirect(...) # insert reverse or url
   errors = form.errors or None # form not submitted or it has errors
   return render(request, 'path/to/template.html',{
          'form': form,
          'errors': errors,
   })

To add a new book or edit one, you should use a ModelForm. Then in that view you'll check if it's a new form or not

book_form = BookForm() # This will create a new book

or

book = get_object_or_404(Book, pk=1)
book_form = BookForm(instance=book) # this will create a form with the data filled of book with id 1