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• This is an example of a basic HTML view without the HTML template.

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• The different is that these views make use of arguments (the request and question_id).
• I think the request should always be placed as the first positional argument.

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• The URL is handled by a Django module named mysite.urls.

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• The question_id is an argument that can be filled depending on the routing. It needs to be the same with the argument provided in the views.py.
• For example url(r"^(?P<_question_id>[0-9]+)/$", views.details, name="detail"), means that the call view function needs to have an argument called _question_id that will be filled into as a parameter for the view function. Below is an example of the view codes.

def details(_request, _question_id):
    question = get_object_or_404(Question, pk=_question_id)

    return render(_request, "polls/detail.html", { "question": question })

• Notice that it has the same argument named after _question_id.
• Example on adding and constructing URL pathing in Django.
• Since the main application is "mysite" everything is taken from there.
• However, in the urls.py in mysite directory has a URL reference into the polls.url.
• The polls/urls.py is the designated URL pathing for every web pages that is related to the poll application.
• Here is the current codes for mysite/urls.py (the main application).

urlpatterns = [
    url(r'^polls/', include("polls.urls")),
    url(r'^admin/', admin.site.urls)
]

• Here is the current codes for polls/urls.py.

app_name = "polls"
urlpatterns = [
    # Example: /polls/.
    url(r"^$", views.index, name="index"),
    #Example: /polls/5/.
    url(r"^(?P<_question_id>[0-9]+)/$", views.details, name="detail"),
    #Example: /polls/5/results/.
    url(r"^(?P<_question_id>[0-9]+)/results/$", views.results, name="results"),
    #Example: /polls/5/vote/.
    url(r"^(?P<_question_id>[0-9]+)/vote/$", views.vote, name="vote"),
]

• Notice that in the mysite/urls.py there is this codes url(r'^polls/', include("polls.urls")), that "import" URL pathing/routing from the polls application.

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• You can put suffix .html in the routing but it is not necessary and is silly.

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• For view, all Django wants is a HTTPResponse or an exception if the view function failed to be called.

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• Example of simple HTTPResponse.
• The call on method HttpResponse() is meant to only render a text into the web view.

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• Then in order for Django to use a HTML template, "templates" folder needs to be created inside the root directory of an application.
• At default the Django will look for "templates" directory to search over HTML template.

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• There is a specific configurations for DjangoTemplates.
• In general Django will look into "templates" directory in the root of every application listed in INSTALLED_APPS.

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• There is a need to create another folder with the same name with the application in the newly created "templates" folder for namespacing.
• And also because Django needs to be able to determine which application use which template in case there are more than templates with the same name.
• In general Django will look into every "template" directories for each application to look after HTML template. This is the reason why namespacing is important!

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• Method template.render() can be used to render HTML template.

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• This is an example of template rendering in Django.
• The latest_question_list is now callable variable in the template called by DjangoTemplates. For example by using {{ latest_question_list }} or in for loop statement like codes below.

{% for question in latest_question_list %}
  {{ question.question_text }}
{% endfor %}

• The codes above will render every question (the text, not the object) to the web browser.
• Similarly, accessing "child" model is possible as well.

{% for choice in question.choice_set.all %}
  {{ choice.choice_text }}
{% endfor %}

• Remember that choice_set is based from the Choice as a model, turned all lower case and then added suffix _set.
• The concept of question.choice_set.all is the same with Python codes question.choice_set.all().
• What I am not sure why it is suffixed as _set instead of _get though.

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• The codes in the screenshot above means to call HTTP request to render a HTML templates using DjangoTemplates.

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• The current result of URL polls that shows all recorded polls.

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• Django has plethora of useful shortcuts.
• These shortcuts can be accessed via django.shortcuts import ....
• For example, in this tutorial we use from django.shortcuts import render.
• render() is a set of function/method to call HTTP request for render.
• Hence, instead of HttpResponse(template.render(context, _request)), with render() it will be just render(_request, "polls/index.html", context).
• The middle parameter is a relative path to where the template is located.
• In general this makes no use of loader and HttpRespose because everything is already packaged in render().
• render() will return HttpResponse object.

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• The <WSGIRequest: GET '/polls/'> is the value from _request.

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• The codes above is an example on how to raise the generic 404 error if routing brings the user to nothing.

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• However, django.shortcuts has get_object_or_404() to let you to search for an database object (cell/document) and if the such object is not exist then automatically return error 404.
• The codes above has the same result with raising error 404 with try and except but with more concise syntax.

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• There is a shortcut to get list as well instead of object, get_list_or_404().
• This one is used when looking through database with filter() instead of return an object with get().
• The get_list_or_404 will return 404 error if the list is empty.

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• There is this philosophical thought that I am not sure what it meant.
• I think the use of django.shortcut is to maintain the independence of model and view layer.
• That, or we need to keep Django manage anything between the model and view layer.

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• As previously written, with the HTML template we can access the data from the "children" model as well.

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• This StackOverflow discussion explains this situation very well, https://stackoverflow.com/questions/32767629/django-dot-lookup-syntax-to-access-variable-attributes.
• Full screenshot.

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• In sense for the DjangoTemplates it will look each variable with these order.
  1. Dictionary lookup, for example foo["bar"].
  2. Attribute lookup, for example foo.bar.
  3. List - index lookup, for example foo[bar].

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• As previously mentioned, the HTML template codes question.choice_set.all is the same with the Python codes question.choice_set.all().

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• When I thought the URL routing is dynamic enough.
• This Django tutorial said that the current URL routings is actually "hard - coded".
• There is more dynamic way on how to make the URL routings. This means that the URL variable is taken from the urls.py.
• This way if there is change necessary for the URL, the developer only needs to change whatever he/she wants to change in the urls.py.

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• Example of URL routings with Regular Expression.
• Here is an example when I need to add "specifics" before the question_id.

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• The same with template. Django take the URL routing into the highest level.
• If there is a same URL routing name then Django will take whichever routing comes first.
• To solve this problem, URL namespace is necessary.
• Add these codes in the polls/urls.py.

app_name = "polls"

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• Then do this in both URL routings and the HTML template.
• Here is the link to the tutorial, https://docs.djangoproject.com/en/1.11/intro/tutorial03/.
• Here is the screenshot.

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