Django 的学习(2) 从adminuser到配置

创建一个superuser

python manage.py createsuperuser
然后是密码邮箱用户名

You should see a few types of editable content: groups and users. They are provided by django.contrib.auth, the authentication framework shipped by Django.

这个模块是由
django.contrib.auth提供的
将polls 导入admin界面
修改
polls/admin.py

from django.contrib import admin

from .models import Question

admin.site.register(Question)

注意models.py 和 admin.py在同一目录下，所以就form .models import的形式
Things to note here:

The form is automatically generated from the Question model.
The different model field types (DateTimeField, CharField) correspond to the appropriate HTML input widget. Each type of field knows how to display itself in the Django admin.
Each DateTimeField gets free JavaScript shortcuts. Dates get a “Today” shortcut and calendar popup, and times get a “Now” shortcut and a convenient popup that lists commonly entered times.

The bottom part of the page gives you a couple of options:

Save – Saves changes and returns to the change-list page for this type of object.
Save and continue editing – Saves changes and reloads the admin page for this object.
Save and add another – Saves changes and loads a new, blank form for this type of object.
Delete – Displays a delete confirmation page.
＃add more view#
首先是polls/views.py
的修改

from . import views

urlpatterns = [
    # ex: /polls/
    url(r'^$', views.index, name='index'),
    # ex: /polls/5/
    url(r'^(?P<question_id>[0-9]+)/$', views.detail, name='detail'),
    # ex: /polls/5/results/
    url(r'^(?P<question_id>[0-9]+)/results/$', views.results, name='results'),
    # ex: /polls/5/vote/
    url(r'^(?P<question_id>[0-9]+)/vote/$', views.vote, name='vote'),
]

看看正则表达式的用法，比较厉害的是
(?P<question_id>[0-9]+)
这里捕获了一个参数，传递给后面的views方法，像这样
detail(request=, question_id='34')
这里是真的正则表达式
所以你可以这么做
url(r'^polls/latest.html$', views.index),
但是很傻

实用的view
polls/views.py
from django.http import HttpResponse
from .models import Question
def index(request):
latest_question_list = Question.objects.order_by('-pub_date')[:5]
output = ', '.join([q.question_text for q in latest_question_list])
return HttpResponse(output)

Leave the rest of the views (detail, results, vote) unchanged

只改变了第一个index的
注意这里用了Question 来调用数据库中的内容了

templates 技术
First, create a directory called templates in your polls directory. Django will look for templates in there.

Your project’s TEMPLATES setting describes how Django will load and render templates. The default settings file configures a DjangoTemplates backend whose APP_DIRS option is set to True. By convention DjangoTemplates looks for a “templates” subdirectory in each of the INSTALLED_APPS.

Within the templates directory you have just created, create another directory called polls, and within that create a file called index.html. In other words, your template should be at polls/templates/polls/index.html. Because of how the app_directories template loader works as described above, you can refer to this template within Django simply as polls/index.html.

Template namespacing

Now we might be able to get away with putting our templates directly in polls/templates (rather than creating another polls subdirectory), but it would actually be a bad idea. Django will choose the first template it finds whose name matches, and if you had a template with the same name in a different application, Django would be unable to distinguish between them. We need to be able to point Django at the right one, and the easiest way to ensure this is by namespacing them. That is, by putting those templates inside another directory named for the application itself.

默认情况下django会检查所有install_app 下面的templates
但是最好再templates下面再加一个与install_app同名的文件，
因为django会默认的将所有tempaltes合并，这么的话要是有同名文件就无法识别了

polls/templates/polls/index.html

{% if latest_question_list %}
    <ul>
    {% for question in latest_question_list %}
        <li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>
    {% endfor %}
    </ul>
{% else %}
    <p>No polls are available.</p>
{% endif %}

这里使用了templates的语法，不是很懂

polls/views.py
from django.http import HttpResponse
from django.template import loader

from .models import Question

def index(request):
latest_question_list = Question.objects.order_by('-pub_date')[:5]
template = loader.get_template('polls/index.html')
context = {
'latest_question_list': latest_question_list,
}
return HttpResponse(template.render(context, request))
这里使用了loader 加载template
context 字典文件 键应该是变量名的字符串，
值是变量值
最后调用加载了template 的loader 的render方法,接受两个参数
返回
from django.shortcuts import render

from .models import Question

def index(request):
latest_question_list = Question.objects.order_by('-pub_date')[:5]
context = {'latest_question_list': latest_question_list}
return render(request, 'polls/index.html', context)
也可以这么写，调用 django.shortcuts 中的render
接受 request template的字符串 context
可以看出来确实查找templates的时候是合并了每一个installed_app的templates的

404的产生#

polls/views.py
from django.http import Http404
from django.shortcuts import render

from .models import Question

...

def detail(request, question_id):
try:
question = Question.objects.get(pk=question_id)
except Question.DoesNotExist:
raise Http404("Question does not exist")
return render(request, 'polls/detail.html', {'question': question})
可以看到except 搞定了一个异常，紧接着我就抛出了一个django.http 中的
Http404
然后就进入了page404

shortcut
这里可以使用 django.shortcuts 中的 get_object_or_404 方法
该方法第一个参数可以是 Django的model
第二个参数
nd an arbitrary number of keyword arguments, which it passes to the get() function of the model’s manager. It raises Http404 if the object doesn’t exist.

Philosophy（哲♂学）
Why do we use a helper function get_object_or_404() instead of automatically catching the ObjectDoesNotExist exceptions at a higher level, or having the model API raise Http404 instead of ObjectDoesNotExist?
Because that would couple the model layer to the view layer. One of the foremost design goals of Django is to maintain loose coupling. Some controlled coupling is introduced in the django.shortcuts module.

There’s also a get_list_or_404() function, which works just as get_object_or_404() – except using filter() instead of get(). It raises Http404 if the list is empty.
差不多，还记的数据库中对Objects model的操作了吗
＃用templates 的语法来玩耍吧#
polls/templates/polls/detail.html

<h1>{{ question.question_text }}</h1>
<ul>
{% for choice in question.choice_set.all %}
    <li>{{ choice.choice_text }}</li>
{% endfor %}
</ul>

dot-lookup syntax是一个什么鬼，但是django用这种语法
奇怪的语法，我打错了尖括号与花括号，还查了5分钟
但是这里不全python的语法
哪里调用的因该是
for chocie in question.choice_set.all()
刚开始的时候，django试图去用 dictionary lookup 结果失败了
然后使用 attribute lookup 成功了
如果还失败就会使用 list-index lookup
Method-calling happens in the {% for %} loop: question.choice_set.all is interpreted as the Python code question.choice_set.all(), which returns an iterable of Choice objects and is suitable for use in the {% for %} tag.

更换hardcode.
修改 index 中的hardcode