Django基礎，Day4 - views 詳解

在Django中，網頁和其他內容是通過視圖傳遞的。每個視圖由一個簡單的Python函數表示,Django將通過檢查請求的URL（准確地說，是域名后面的部分URL）來選擇一個視圖。

例如，用戶在瀏覽器中訪問 <<domain>>/newsarchive/<year>/<month>/  diango的URLConfs 將請求URL與對應的views function 匹配，調用view function 進行數據處理，然后選擇對應的template模板進行渲染展示或直接數據返回。

 

在我們的poll app中，我們將會創建以下四個視圖views：

• Question “index” page – displays the latest few questions.
• Question “detail” page – displays a question text, with no results but with a form to vote.
• Question “results” page – displays results for a particular question.
• Vote action – handles voting for a particular choice in a particular question.

編寫views

polls/views.py:

from django.http import HttpResponse


# Create your views here.
def index(request):
    return HttpResponse("Hello, world. You're at the polls index.")


def detail(request, question_id):
    return HttpResponse("You're looking at question %s." % question_id)


def results(request, question_id):
    response = "You're looking at the results of question %s."
    return HttpResponse(response % question_id)


def vote(request, question_id):
    return HttpResponse("You're voting on question %s." % question_id)

綁定URL與Views

polls/urls.py:

from django.conf.urls import url
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'),
]

URLconfs 中，正則表達式中的分組()作為參數傳遞給view，如url(r'^(?P<question_id>[0-9]+)/$', views.detail, name='detail')

假如請求url為 polls/34/  相當於調用detail(request,question_id='34')

分別訪問一下url可見調用不同的view 函數進行相應

http://localhost:8000/polls/

http://localhost:8000/polls/34/

http://localhost:8000/polls/34/results/

http://localhost:8000/polls/34/vote/

編寫Views的數據庫處理邏輯

view的主要工作：獲取請求內容，調用數據庫model獲取數據庫數據，調用業務處理Model邏輯處理，將處理結果渲染到指定的模板template中，響應response到客戶端瀏覽器

創建 polls/templates,django會在在app目錄下查找templates目錄作為模板路徑

創建 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.

（當然templates下不創建polls，模板路徑調用index.html 也可以，但是強烈不建議這樣，因為避免出現不同的app中有相同名稱的模板文件時讀取區分不出來）

{% 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 %}

更新 index view in polls/views.py：

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)

訪問 http://localhost:8000/polls/ 

編寫Views 404異常

更新detail view in polls/views.py：

def detail(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/detail.html', {'question': question})

get_object_or_404(),get_list_or_404() 當獲取不到對象時，返回404頁面

訪問 http://localhost:8000/polls/34/

使用template模板

添加 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>

django模板系統使用雙大括號訪問變量屬性，如{{question.question_text}},

django模板中，使用 {%  %}   將原生pyton語句包含起來，其中以上實例中，使用了for循環：{% for %} {% endfor %}

訪問 http://localhost:8000/polls/1

 

修改template模板中的hardcoded URLs，統一使用{% url %} 標簽替換

如polls/index.html 中的  <li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li> 

修改為：<li><a href="{% url 'detail' question.id %}">{{ question.question_text }}</a></li>

這種URL 查找方式是通過polls.urls 中的name來匹配，如：

mysite/urls.py：

    url(r'^polls/', include('polls.urls', namespace="polls")),

polls/urls.py:

# the 'name' value as called by the {% url %} template tag

    url(r'^(?P<question_id>[0-9]+)/$', views.detail, name='detail'),

 

 添加 URL namespace

如上例，使用{% url 'detail' %} 可以根據polls.urls 中的name='detail' 來匹配。如果在同一個project下有多個app，其中都有name='detail' 時,又該如何匹配views呢？

解決方法是，添加namespace到URLconf中，如在polls/urls.py 中添加： app_name = 'polls'

則可以在模板中修改{% url 'detail' %} 為 {% url 'polls:detail' %}

訪問：http://localhost:8000/polls/

點擊“what's up” 鏈接

 

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