How to do it...

To complete this recipe, execute the following two steps:

1. Modify the IdeaForm model form as follows:

# myprojects/apps/ideas/forms.py
from django import forms
from .models import Idea

class IdeaForm(forms.ModelForm):
    class Meta:
        model = Idea
        exclude = ["author"]

    def __init__(self, request, *args, **kwargs):
        self.request = request
        super().__init__(*args, **kwargs)

    def save(self, commit=True):
        instance = super().save(commit=False)
        instance.author = self.request.user
        if commit:
            instance.save()
            self.save_m2m()
        return instance

2. Modify the view to add or change the ideas:

# myproject/apps/ideas/views.py
from django.contrib.auth.decorators import login_required
from django.shortcuts import render, redirect, get_object_or_404

from .forms import IdeaForm
from .models import Idea


@login_required
def add_or_change_idea(request, pk=None):
    idea = None
    if pk:
        idea = get_object_or_404(Idea, pk=pk)

    if request.method == "POST":
        form = IdeaForm(request, data=request.POST, 
         files=request.FILES, instance=idea)
       
        if form.is_valid():
            idea = form.save()
            return redirect("ideas:idea_detail", pk=idea.pk)
    else:
        form = IdeaForm(request, instance=idea)

    context = {"idea": idea, "form": form}
    return render(request, "ideas/idea_form.html", context)