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Views view

Summary of view

Views are view functions, transaction functions that receive Web requests and return web responses
A response is anything that meets the requirements of the HTTP protocol, including JSON, String, HTML, and so on
This chapter ignores transaction processing and focuses on how to handle the return result

Other simple views

Django. HTTP gives us many simple views similar to HttpResponse, as we know by looking at the django. HTTP code
This type of view is used in much the same way and can be returned to the browser as direct feedback via a return statement
Http404 is an Exception subclass, so raise is required

HttpResponse,

methods
- Init: Instantiate an HttpResponse object using web page content
- Write (Content): Write as a file
- Flush (): Outputs the cache as a file
- Set_cookie (key, value= “, max_age=None, Expires =None): Sets the cookie
  - Both key and value are strings
  - Max_age is an integer that expires after a specified number of seconds
  - An expires is a datetime or timedelta object at which the session will expire,
  - Choose max_age or Expires
  - If the expiration time is not specified, it will expire in two weeks
- Delete_cookie (key): Deletes the Cookie of the key, and nothing happens if the key does not exist

HttpResponseRedirect

Redirection, redirect the server
The first argument to the constructor specifies the address to be redirected to

The Request object

The Request is introduced
- After receiving the HTTP request, the server creates an HttpResponse object based on the packet
- The first argument to the view function is an HttpResponse object
- An API for HttpResponse objects is defined in the Django. HTTP module
attribute
- The properties below are read-only unless otherwise noted
- Path: A string representing the full path to the requested page, excluding the domain name
- Method: A string representing the HTTP method used in the request. Common values include: ‘GET’, ‘POST’
- Encoding: A string that specifies the encoding method of the submitted data
  - If None, the browser’s default setting is used, which is generally UTF-8
  - This property is writable and can be modified to modify the use of access form data
- GET: a dictionary-like object that contains all the parameters of the GET request
- POST: A dictionary-like object that contains all the parameters of the POST request
- FILES: a dictionary-like object that contains all uploaded FILES
- COOKIES: A standard Python dictionary containing all COOKIES with strings of keys and values
- Session: a dictionary-like object that is readable and writable and represents the current session,
  - This is only available if Django has session support enabled
  - See “State holding” for details.
methods
- Is_ajax (): Returns True if the request was initiated via XMLHttpResponse

QueryDict object

Defined in django. HTTP. QueryDict
The GET and POST properties of the Request object are QueryDict objects
Unlike Python dictionaries, objects of type QueryDict deal with multiple values for the same key
Method get(): gets the value based on the key
- Only one value of the key can be obtained
- If a key has multiple values, get the last value
Method getList (): gets values based on keys
- Multiple values of a key can be obtained by returning the key values as a list

The GET property

Objects of type QueryDict
Contains all the parameters of the GET request
Corresponds to the parameter in the URL request address, located at? behind
The parameter format is key-value pair, that is, key1 = value1
Multiple parameters are connected with am&, for example, key1=value1&key2=value2
Keys are determined by the developer, and values are mutable
Case/views/v12_get

def v12_get(request) :
    rst = ""
    for k,v in request.GET.items():
        rst += k + '-->' + v
        rst += ', '

    return HttpResponse("Get value of Request is {0}".format(rst))
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POST properties

Objects of type QueryDict
Contains all parameters of the POST request mode
Corresponds to a control in the Form form
Controls in the form must have a name attribute, where name is the key and value is the value
- Checkbbox has multiple values with one key
Keys are determined by the developer, and values are mutable

Case/views/v9_post

Set the template position in settint
Set the urls and functions of the GET page

def v9_post(request) :
    rst = ' '
    for k, v in request.POST.items():
        rst += k + '- >' + v
        rst += ', '
    return HttpResponse("Get value of POST is {0}".format(rst))
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Writing views manually

The experiment purpose
- Write view handlers manually using Django shortcuts
- Understand how views work while writing
Analysis of the
- Django wraps all request information into a request
- Django connects the request to the event handler via the urls module and passes the request as a parameter
- In the corresponding handler, we need to do two parts
  - Deal with business
  - To wrap and return the result, we can either use HttpResponse or handle this function ourselves
- This case does not cover business processing, but focuses on how to render the result and return it
render(request, template_name[, context][, context_instance][, content_type][, status][, current_app][, dirs][, using])
- Returns an HttpResponse object for render and, using a template and a given context
- Request: An incoming request from Django
- Template_name: indicates the template name
- Content_instance: Context
- See ruochen_views/teacher_app/views/render_test for an example
```
def rander_test(request) :
    # Environment variables
    # c = dict()
    rsp = render(request, "render.html")
    # rsp = HttpResponse(request, "render.html")
    return rsp
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```
render_to_response
- Render the given template according to the given context dictionary. Returns the rendered HttpResponse
Built-in system view
- Built-in system view, which can be used directly
- 404
  - default.page_not_found(request, template_name=’404.html’)
  - Triggered when the system raises Http404
  - The default is to pass the request_PATH variable to the template, which is the URL that caused the error
  - DEBUG=True does not call 404, but instead sends debugging messages
  - The 404 view is passed a RequestContext object and can access variables provided by the template context handler (MEDIA_URL, etc.)
- 500(server error)
  - defaults.server_error(request, template_name=’500.html’)
  - DEBUG=False is required, otherwise not called
- 403 (HTTP Forbidden) View
  - defaults.permission_denied(request, template_name=’403.html’)
  - Triggered by PermissionDenied
- 400 (Bad Request) view
  - defaults.bad_request(request, template_name=’400.html’)
  - DEBUG=False

Class-based view

A quick word about class-based views

The advantages and differences between and function-based views:
- HTTP methods of methode can have their own methods and do not need to use conditional branches to solve
- OOP techniques can be used (such as mixins)
An overview of the
- The core is to allow different instance methods to correspond to different HTTP request methods, bypassing conditional branching implementations
- The as_view function, which creates an instance and calls the dispatch method, dispatches the request according to the request method, if the
Method, which is not defined, raises HttpResponseNotAllowed
Class attribute usage
- Overrides directly at class definition time
- When calling as_view, use last night arguments directly, for example:
```
urlpatterns = [
    url(r'^about/', GreetingView.as_view(greeting="G'day")),
    ]
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```
There are roughly three ways to extend class-based views: Mixin, decorated AS_view, and decorated dispatch
The use of a Mixin
- A form of multiple inheritance in which actions and attributes from Frey are grouped together
- Solve multiple inheritance problems
- View subclasses can only be inherited single-inheritance, and multiple inheritance causes unpredictability
- Problems with multiple inheritance:
  - Complicated structure
  - Fuzzy priorities
  - Functional conflict
- The solution
  - Specification inheritance – Java Interface
  - Implement inheritance – Python, Ruby

Decorate in URLconf

from django.contrib.auth.decorators import login_required, permission_required
from django.views.generic import TemplateView

from .views import VoteView

urlpatterns = [
    url(r'^about/', login_required(TemplateView.as_view(template_name="secret.html"))),
    url(r'^vote/', permission_required('polls.can_vote')(VoteView.as_view())),
]

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Decoration class

Class methods, unlike stand-alone methods, do not apply a decorator directly. Instead, use methode_decorator

from django.contrib.auth.decorators import login_required
from django.utils.decorators import method_decorator
from django.views.generic import TemplateView

class ProtectedView(TemplateView):
    template_name = 'secret.html'

    @method_decorator(login_required)
    def dispatch(self, *args, **kwargs):
        return super(ProtectedView, self).dispatch(*args, **kwargs)
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The relevant code

The relevant code used in the view section is as follows

urls.py

from django.conf.urls import include, url
from django.contrib import admin

from teacher_app import views as v

urlpatterns = [
    # Examples:
    # url(r'^$', 'ruochen_views.views.home', name='home'),
    # url(r'^blog/', include('blog.urls')),

    url(r'^admin/', include(admin.site.urls)),

    url(r'^teacher/', v.teacher),
    url(r'^v2_exp/', v.v2_exception),

    url(r'^v10_1/', v.v10_1),
    url(r'^v10_2/', v.v10_2),
    url(r'^v11_hello/', v.v11, name='v11'),

    url(r'^v12/', v.v12_get),
    url(r'^v9_get/', v.v9_get),
    url(r'^v9_post/', v.v9_post),

    url(r'render_test/', v.rander_test),
    url(r'render2_test/', v.rander2_test),
    url(r'render3_test/', v.rander3_test),

    url(r'render1_to_res/', v.render4_test),

    url(r'^get404/', v.get404),
]

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views.py

from django.shortcuts import render, render_to_response
from django.http import HttpResponse, Http404, HttpResponseRedirect
from django.core.urlresolvers import reverse
# Create your views here.

def teacher(r) :
    return HttpResponse('This is a view of teacher')

def v2_exception(r) :
    raise Http404
    return HttpResponse('OK')

def v10_1(r) :
    return HttpResponseRedirect(reverse('v11'))

def v10_2(r) :
    return HttpResponseRedirect(reverse('v11'))

def v11(r) :
    return HttpResponse('V11 access return')

def v12_get(request) :
    rst = ""
    for k,v in request.GET.items():
        rst += k + '-->' + v
        rst += ', '

    return HttpResponse("Get value of Request is {0}".format(rst))

def v9_get(request) :
    Render a template and return
    return render_to_response('for_post.html')

def v9_post(request) :
    rst = ' '
    for k, v in request.POST.items():
        rst += k + '- >' + v
        rst += ', '
    return HttpResponse("Get value of POST is {0}".format(rst))

def rander_test(request) :
    # Environment variables
    # c = dict()
    rsp = render(request, "render.html")
    # rsp = HttpResponse(request, "render.html")
    return rsp

def rander2_test(request) :
    # Environment variables
    c = dict()

    c['name'] = "ruochen"
    c['name2'] = "ruochen2"
    c['name3'] = "ruochen3"

    rsp = render(request, "render2.html", context=c)
    return rsp

def rander3_test(request) :

    from django.template import loader

    # get template
    t = loader.get_template('render2.html')
    print(type(t))

    r = t.render({"name": "ruochen"})
    print(type(r))
    return HttpResponse(r)

def render4_test(request) :
    # feedback to m template render2.html
    rsp = render_to_response("render2.html", context={"name": "ruochen"})
    return rsp

def get404(request) :
    from django.views import defaults
    return defaults.page_not_found(request, template_name="render.html")
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templates

for_post.html

<html>
<head>
    <title>Title</title>
</head>
<body>
<form method="post" action="/v9_post/">Name:<input type="text" name="uname"/><br>Password:<input type="password" name="upwd"/><br>Gender:<input type="radio" name="ugender" value="1"/>male<input type="radio" name="ugender" value="0"/>female<br>Hobbies:<input type="checkbox" name="uhobby" value="Just the rice"/>Just a meal<input type="checkbox" name="uhobby" value="Jump"/>Jump off a building<input type="checkbox" name="uhobby" value="Drinking"/>drinking<input type="checkbox" name="uhobby" value="Jump"/>Climbing the mountain<br>
    <input type="submit" value="Submit"/>
</form>
</body>
</html>
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render.html

<! DOCTYPEhtml>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<h1>Render example by ruochen</h1>

</body>
</html>
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render2.html

<! DOCTYPEhtml>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<h1>WebPage for rander with {{name}}</h1>

</body>
</html>
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settings.py

"" Django Settings for ruochen_views project. Generated by 'django-admin startproject' using Django 1.8. for more information on this file, See https://docs.djangoproject.com/en/1.8/topics/settings/ For a full list of Settings and their values. See "https://docs.djangoproject.com/en/1.8/ref/settings/" "

# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
import os

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/1.8/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = 'a^-vz9v! e2ks%m=d*&fu$r)qc42vpgkqny9jl36plg$(3jtp#q'

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = ["*"]


# Application definition

INSTALLED_APPS = (
    'django.contrib.admin'.'django.contrib.auth'.'django.contrib.contenttypes'.'django.contrib.sessions'.'django.contrib.messages'.'django.contrib.staticfiles'.'teacher_app',
)

MIDDLEWARE_CLASSES = (
    'django.contrib.sessions.middleware.SessionMiddleware'.'django.middleware.common.CommonMiddleware'.# 'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware'.'django.contrib.auth.middleware.SessionAuthenticationMiddleware'.'django.contrib.messages.middleware.MessageMiddleware'.'django.middleware.clickjacking.XFrameOptionsMiddleware'.'django.middleware.security.SecurityMiddleware',
)

ROOT_URLCONF = 'ruochen_views.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates'.'DIRS': [os.path.join(BASE_DIR, "templates")].'APP_DIRS': True.'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug'.'django.template.context_processors.request'.'django.contrib.auth.context_processors.auth'.'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'ruochen_views.wsgi.application'


# Database
# https://docs.djangoproject.com/en/1.8/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3'.'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),}}# Internationalization
# https://docs.djangoproject.com/en/1.8/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_L10N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/1.8/howto/static-files/

STATIC_URL = '/static/'

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Django Views | Python Theme Month

Views view

Summary of view

Other simple views

HttpResponse,

HttpResponseRedirect

The Request object

QueryDict object

The GET property

POST properties

Writing views manually

Class-based view

The relevant code

Django Views | Python Theme Month

Views view

Summary of view

Other simple views

HttpResponse,

HttpResponseRedirect

The Request object

QueryDict object

The GET property

POST properties

Writing views manually

Class-based view

The relevant code

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