分页组件与CBV

一. 自定义分页

1.准备工作

(1).首先在models.py中创建一张book表用来存储数据

 from django.db import models
 class Book(models.Model):
     title=models.CharField(max_length=32)
     price=models.CharField(max_length=32)
     def __str__(self):
         return self.title

(2)在index.html中创建大量数据

 for j in range(100):
     result=""
     for i in range(6):
         up=chr(random.randint(65,90))
         low=chr(random.randint(97,122))
         num=str(random.randint(0,9))
         choice=random.choice([up,low,num])
         result=choice+result
     Book.objects.create(title=result,price=j*j)
 return HttpResponse("ok")

2.在urls.py中添加一个路径

 urlpatterns = [
     path('admin/', admin.site.urls),
     path('index/', views.index),
 ]

3.视图函数index的准备工作:在一个新的脚本中编写Pagination类

 class Pagination():
     def __init__(self, current_page_num, all_count, request, per_page_num=5, pager_count=11):
         """
         封装分页相关数据
         :param current_page_num: 当前访问页的数字
         :param all_count:    分页数据中的数据总条数
         :param per_page_num: 每页显示的数据条数
         :param pager_count:  最多显示的页码个数
         """
         try:
             current_page_num = int(current_page_num)
         except Exception as e:
             current_page_num = 1
         if current_page_num < 1:
             current_page_num = 1
         self.current_page_num = current_page_num
         self.all_count = all_count
         self.per_page_num = per_page_num
         all_pager, tmp = divmod(all_count, per_page_num)
         if tmp:
             all_pager += 1
         self.all_pager = all_pager
         self.pager_count = pager_count
         self.page_count_half = int((pager_count - 1) / 2)
         import copy
         self.params = copy.deepcopy(request.GET)

     @property
     def start(self):
         return int((self.current_page_num - 1) * self.per_page_num)

     @property

     def end(self):
         return int(self.current_page_num * self.per_page_num)

     def page_html(self):
         if self.all_pager<=self.pager_count:
             page_start=1
             page_end=self.all_pager+1
         else:
             if self.current_page_num<=self.page_count_half:
                 page_start=1
                 page_end=self.pager_count+1
             else:
                 if self.current_page_num >(self.all_pager-self.page_count_half):
                     page_start=self.all_pager-self.pager_count+1
                     page_end=self.all_pager+1
                 else:
                     page_start=self.current_page_num-self.page_count_half
                     page_end=self.current_page_num+self.page_count_half+1
         page_html_list=[]
         first_page='<li><a href="?page=%s">首页</li>' % 1
         page_html_list.append(first_page)
         if self.current_page_num<=1:
             prev_page="<li class='disabled'><a href='#'>上一页</a></li>"
         else:
             prev_page = "<li ><a href='?page=%s'>上一页</a></li>" % (self.current_page_num-1)
         page_html_list.append(prev_page)
         for i in range(page_start,page_end):
             self.params["page"]=i
             if i==self.current_page_num:
                 temp="<li class='active'><a href='?%s'>%s</a></li>" % (self.params.urlencode(),i)
             else:
                 temp = "<li><a href='?%s'>%s</a></li>" % (self.params.urlencode(), i)
             page_html_list.append(temp)
         if self.current_page_num>=self.all_pager:
             next_page="<li class='disabled'><a href='#'>下一页</a></li>"
         else:
             next_page = "<li ><a href='?page=%s'>下一页</a></li>" % (self.current_page_num+1)
         page_html_list.append(next_page)
         last_page = '<li><a href="?page=%s">尾页</li>' % (self.all_pager)
         page_html_list.append(last_page)
         return "".join(page_html_list)

4.index视图函数

 from django.shortcuts import render
 from app01.models import Book
 def index(request):
     from app01.page import Pagination
     current_page_num = request.GET.get("page")
     book_list = Book.objects.all()
     pagination=Pagination(current_page_num,book_list.count(),request)
     booklist=book_list[pagination.start:pagination.end]
     return render(request,"index.html",locals())

5.index.html页面

 <!DOCTYPE html>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <title>Title</title>
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

 </head>
 <body>
 <ul>
     {% for book in booklist %}
     <li>名称:{{ book.title }} 价格:{{ book.price }}</li>
     {% endfor %}
 <nav aria-label="Page navigation">
   <ul class="pagination">
    {{ pagination.page_html|safe }}
   </ul>
 </nav>
 </ul>
 </body>
 </html>

二.保存搜索条件

1.原码部分:

为什么request.get得到的queryset不能更改,但是copy之后的queryset可以更改

 class QueryDict(MultiValueDict):

 _mutable = True

 #mutable是可更改的意思,默认为true,可以更改
 _encoding = None
 def __init__(self, query_string=None, mutable=False, encoding=None):

 Pass#当实例化方法执行之后mutable更改为False,不可以更改

    def __copy__(self):
        result = self.__class__('', mutable=True, encoding=self.encoding)
        for key, value in self.lists():
           result.setlist(key, value)
        return result
     def __deepcopy__(self, memo):
        result = self.__class__('', mutable=True, encoding=self.encoding)
        memo[id(self)] = result
        for key, value in self.lists():
            result.setlist(copy.deepcopy(key, memo), copy.deepcopy(value, memo))
        return result

 #当执行深拷贝或浅拷贝方法时,mutable又被更改为true,可以更改

2.urlencode()方法

拷贝之后可以使用urlencode方法

params=copy.deepcopy(request.GET)

print(params.urlencode())

得到的是搜索条件没有拆包urlencode模式: page=10&a=1

3.保存搜索条件的方法

(1)调用该类时,把request传进去

pagination=Pagination(current_page_num,book_list.count(),request)

(2)在实例化时深拷贝request.GET

import copy
self.params = copy.deepcopy(request.GET)

(3)将搜索条件全都放到parmas字典中,利用urlencode方法,拼接成路径的urlencode模式,并放到相应的位置

 for i in range(page_start,page_end):
     self.params["page"]=i
     if i==self.current_page_num:
         temp="<li class='active'><a href='?%s'>%s</a></li>" % (self.params.urlencode(),i)
     else:
         temp = "<li><a href='?%s'>%s</a></li>" % (self.params.urlencode(), i)
     page_html_list.append(temp)

三.CBV

FBV:function based view,基于函数的视图

CBV:class based view,基于类的视图

1.cbv流程

(1)在视图类创建视图类

 from django.shortcuts import render,HttpResponse
 from django.views import View
 class LoginView(View):
     def get(self,request):
         return render(request,"login.html")
     def post(self,request):
         print("post")
         return HttpResponse("ok")
     def delete(self,request):
         pass
     def put(self,request):
         pass

(2) 在urls.py中为该类创建相应的分支

path('login/', views.LoginView.as_view()),

(3)创建视图类中需要的HTML

 <!DOCTYPE html>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <title>Title</title>
 </head>
 <body>
 <form action="" method="post">
     {% csrf_token %}
     用户名: <input type="text" name="user">
     密码: <input type="text" name="pwd">
     <input type="submit">
 </form>
 </body>
 </html>2.原码部分

2.原码部分

(1)View中的as_view

 @classonlymethod

 def as_view(cls, **initkwargs):

 #cls代表当前类
     for key in initkwargs:
         if key in cls.http_method_names:
             raise TypeError("You tried to pass in the %s method name as a "
                             "keyword argument to %s(). Don't do that."
                             % (key, cls.__name__))
         if not hasattr(cls, key):
             raise TypeError("%s() received an invalid keyword %r. as_view "
                             "only accepts arguments that are already "
                             "attributes of the class." % (cls.__name__, key))

     def view(request, *args, **kwargs):
         self = cls(**initkwargs)

 #self代表LoginView的实例对象
         if hasattr(self, 'get') and not hasattr(self, 'head'):
             self.head = self.get
         self.request = request
         self.args = args
         self.kwargs = kwargs
         return self.dispatch(request, *args, **kwargs)

 #分发方法
     view.view_class = cls
     view.view_initkwargs = initkwargs

     update_wrapper(view, cls, updated=())

     update_wrapper(view, cls.dispatch, assigned=())
     return view

(3) dispatch()

 def dispatch(self, request, *args, **kwargs):
     if request.method.lower() in self.http_method_names:

 #判断request.mothod是否在self.http_method_names中

 #http_method_names = ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace']

 #http协议中主要支持的请求方式
         handler = getattr(self, request.method.lower(), self.http_method_not_allowed)

 #利用反射去LoginView中找其中的某个方法(get)
     else:
         handler = self.http_method_not_allowed
     return handler(request, *args, **kwargs)

 #执行了找到的那个方法(get)