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django体验（二）跟着文档走 part3+part4

阅读：531 发布：2018-08-16 作者：lypeng

django体验

官方文档地址：`https://docs.djangoproject.com/en/2.1/intro/tutorial03/`

[TOC]

# 四、更多function与模板使用( part3)

## 1. views.py
```
from django.http import HttpResponse
from .models import Question

def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5] #这里的-号是降序,写+报错，不加任何符号是升序
    output = ', '.join([q.question_text for q in latest_question_list])
    return HttpResponse(output)
def detail(request,question_id):
    return HttpResponse("question id is %s." % question_id)
```

## 2. urls.py新增如下
```
    path('<int:question_id>/', views.detail, name='detail'),
    # ex: /polls/5/results/
    path('<int:question_id>/results/', views.results, name='results'),
    # ex: /polls/5/vote/
    path('<int:question_id>/vote/', views.vote, name='vote'),
```

## 3. templates
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 %}
```

## 4. 修改views.py调用模板并渲染
有以下两种方式
```
    template = loader.get_template('polls/index.html')
    return HttpResponse(template.render(context, request))
```

```
from django.shortcuts import render
...
def index(request):
    ...
    return render(request, 'polls/index.html', context)
```

## 5.抛出404
```
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})
```

detail.html
```
{{ question.id }}
<br/>
{{ question.question_text }}
<br/>
{{ question.pub_date }}
```

更便捷方法get_object_or_404
`question = get_object_or_404(Question, pk=question_id)`
注意，这是个方法，传递两个参数
相似函数：
`question_list = get_list_or_404(Question)`，还不清楚limit怎么传？

## 6.关闭debug设置
```
DEBUG = False
ALLOWED_HOSTS = ['127.0.0.1'] # 必须设置，否则报错
```
还是打开好，否则报个500错误，我都不知道是什么

## 7.URL地址重定义
a.index.html
采用{% url 'detail' question.id %}
比/polls/{{ question.id }}/更灵活

b.polls/urls.py
path('<int:question_id>/', views.detail, name='detail'),

path的第一个参数可以自定义，而不用改模板与views

## 8.命名空间
urls.py新增app_name
`app_name = 'polls'`
index.html改写
`{% url 'polls:detail' question.id %}`

## 9.sqlite的查询与插入
和mysql一样，select insert

![](/django/4.jpg)

# 五、表单与自带的view（part4）
amend 英 [ə'mend] 修正
generic 英 [dʒɪ'nerɪk] 公共的

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use generic views less code is better
write less do more
## 1. 表单与处理

detail.html,提交到vote方法
```
<form action="{% url 'polls:vote' question.id %}" method="post">
{% csrf_token %}
{% for choice in question.choice_set.all %}
    <input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}">
    <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br>
{% endfor %}
<input type="submit" value="Vote">
</form>
```

views.py vote方法处理用户提交
```
def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice.",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))
```

## 2.使用django自带的view
a.修改urls.py的四个path
```
    path('', views.IndexView.as_view(), name='index'),
    path('<int:pk>/', views.DetailView.as_view(), name='detail'),
    path('<int:pk>/results/', views.ResultsView.as_view(), name='results'),
    path('<int:question_id>/vote/', views.vote, name='vote')
```
b.修改views.py方法
```
from django.http import HttpResponseRedirect
from django.shortcuts import get_object_or_404, render
from django.urls import reverse
from django.views import generic
from .models import Choice, Question

class IndexView(generic.ListView):
    template_name = 'polls/index.html'
    context_object_name = 'latest_question_list'
    def get_queryset(self):
        return Question.objects.order_by('-pub_date')[:5]

class DetailView(generic.DetailView):
    model = Question
    template_name = 'polls/detail.html'

class ResultsView(generic.DetailView):
    model = Question
    template_name = 'polls/results.html'

def vote(request, question_id):
    #not change
```

访问，效果一样，但是这里面的东西，自带的一些属性、变量、方法等，需要记忆

>1.DetailView默认使用polls/question_detail.html,template_name自定义
>2.DetailView需要一个主键，命名为pk
>3.context_object_name与get_queryset是自带的属性与方法

------本文结束感谢阅读------

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