A continuation of 3 where Django beginners create simple apps. Last time, I created C of CRUD, that is, Create part with Class-based-view. This time I'd like to rewrite Class-based-view to Function-view and follow how Django works by comparing the two.
-Django Beginners Create Easy Apps 1 --Preparation-Overview of Django-Creating models.py -Django beginners make simple apps 2 --Implementation of Read part (creation of urls.py, views.py, template file) -Django beginners make simple apps 3 --Implementation of Create part (creation of form.py etc.) --Django Beginners make simple apps 4 (← Now here) --Comparison of Class-based-view and Function-view --Django Beginners make simple apps 5 (Completed) --Implementation of Update part and Delete part
Ubuntu 20.04 LTS Python 3.8.2 Django 3.02
The project name is config and the app name is myapp. In other words, the following two commands have been executed
(myenv)$ django-admin startproject config .
(myenv)$ python manage.py startapp myapp
The templates directory is created in the same hierarchy as manage.py, and setting.py has also been modified. (See "Beginners Create Easy Apps 1")
index_view
class IndexView(generic.ListView):
template_name = 'myapp/index.html'
context_object_name = 'movie_list'
queryset = Movie.objects.all()
#Below is the Function-view
def index(request):
movie_list = Movie.objects.all()
return render(request, 'myapp/index.html', {'movie_list': movie_list})
Actually it ended in 2 lines ... Function-view has shorter code. What you are doing
When a page is requested, Django creates an HttpRequest object that contains metadata about the request. Django then passes HttpRequest as the first function of the view function to load the appropriate view. Every view should return an HttpResponse object.
What is the argument request? Who is requesting what? I was wondering, but the identity of ** request was an object (instance) ** of HttpRequest.
Combines a given template with a given context dictionary and returns an HttpResponse object with that rendered text.
The render function will format the dictionary type data into an HTML file and display it. ** The final thing that comes out with render () is the HttpResponse object (instance). ** **
Each non-abstract Model class must have a Manager instance added to it. Django ensures that in your model class you have at least a default Manager specified. If you don’t add your own Manager, Django will add an attribute objects containing default Manager instance.
** There is a thing called Manager to pull the data in the model (database), and its name is objects. ** So Movie.objects.all () means "Movie objects (Manager), bring all the data!".
detail_view
class MovieDetailView(generic.DetailView):
model = Movie
template_name = 'myapp/detail.html'
#Function from here-view
def moviedetail(request, pk):
m = Movie.objects.get(pk=pk)
return render(request, 'myapp/detail.html', {'movie': m})
Only two lines were needed here. The pk in the(request, pk)part is the<int: pk>of thepath ('movie / <int: pk> /',described in urls.py. This is changed. Yes. If you change the url to <int: movie_id>, change it to (request, movie_id). What you're doing with this function is
register_director_view
class RegisterDirectorView(generic.CreateView):
model = Director
form_class = DirectorForm
template_name = 'myapp/register.html'
def get_success_url(self):
return reverse('myapp:registermovie')
#Function from here-view
def registerdirector(request):
if request.method == "POST":
form = DirectorForm(request.POST)
if form.is_valid():
d = form.save(commit=False)
d.save()
return redirect('myapp:registermovie')
else:
form = DirectorForm()
return render(request, 'myapp/register.html', {'form': form})
The big difference between Class-based-view and Function-view is here at CreateView. Function-view is easier to understand in order to understand the mechanism.
-IT Glossary that makes you feel like you understand even if you don't understand it --HTTP Request Methods -Explanation of the difference between POST and GET in django [There are also specific examples]
The browser communicates with the server via HTTP, but the method is POST. Actually, there is a description of <form method =" POST "> in register.html, which means that when the save button is pressed, the data will be sent as POST, which is entwined with this line.
-Create your first Django app, part 4
request.POST is a dictionary-like object. You can specify the key to access the data you sent. In this case, request.POST ['choice'] returns the ID of the selected choice as a string. The value of request.POST is always a string.
In other words, if the data entered in request.POST is included. It means that an object called form is created by applying it to DirectorForm.
The primary task of a Form object is to validate data. With a bound Form instance, call the is_valid() method to run validation and return a boolean designating whether the data was valid:
Whether an object called form is valid. If there is an input omission, it will play with this. I didn't know the terms validation (checking if the data I entered was correct) and cleaning the data (formatting the data into an easy-to-use form), so at first I was sick.
-Django, note of commit = False in form set
This save() method accepts an optional commit keyword argument, which accepts either True or False. If you call save() with commit=False, then it will return an object that hasn’t yet been saved to the database. In this case, it’s up to you to call save() on the resulting model instance. This is useful if you want to do custom processing on the object before saving it, or if you want to use one of the specialized model saving options. commit is True by default.
The form containing the data is saved to an object called d, but it is not yet in the database. I wondered why I was doing this, but it seems that I may add data to this form later and save it in the database again. Is it something like temporary storage? Then, when it is finally saved in the database with d.save () on the next line.
redirect () says "Fly to the address in ()", and below else says "Create an empty form and render it in register.html". If you use the knowledge you learned in this way, you will be able to read more and more code. I'm glad that I have evolved.
register_movie_view
class RegisterMovieView(generic.CreateView):
model = Movie
form_class = MovieForm
template_name = 'myapp/register.html'
def get_success_url(self):
return reverse('myapp:movie_detail', kwargs={'pk': self.object.pk })
#Function from here-view
def registermovie(request):
if request.method == "POST":
form = MovieForm(request.POST)
if form.is_valid():
m = form.save(commit=False)
m.save()
return redirect('myapp:movie_detail', pk=m.pk)
else:
form = MovieForm()
return render(request, 'myapp/register.html', {'form': form})
The code is almost the same as last time. If you dare to say it, it's the redirect ('myapp: movie_detail', pk = m.pk) part, but does it mean "fly the pk of the object m as the pk of the movie_detail"?
writing_log_view
class WritingLogView(generic.CreateView):
model = Log
form_class = LogForm
template_name = 'myapp/register.html'
def get_success_url(self):
return reverse('myapp:movie_detail', kwargs={'pk': self.object.movie.pk })
#Function from here-view
def writinglog(request):
if request.method == "POST":
form = LogForm(request.POST)
if form.is_valid():
l = form.save(commit=False)
l.save()
return redirect('myapp:movie_detail', pk=l.movie.pk)
else:
form = LogForm()
return render(request, 'myapp/register.html', {'form': form})
The code is almost the same. "I can read! I can read!" (By Muska)
Class-based-View will be easier to write in the end, but Function-view is easier to understand the mechanism and I feel that I can reach the details. Is it like an automatic car and a manual car? No, if you rewrite it to Function-view, it will not work unless you rewrite urls.py properly, so it's not bad. Next time, we plan to implement CRUD UD, that is, Update and Delete. It's probably easier to understand if you write the code side by side like this time. If you have any mistakes, please point out and give us guidance. Is the goal close ...?
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