Django中提供了“信號(hào)調(diào)度”，用于在框架執(zhí)行操作時(shí)解耦。通俗來講，就是一些動(dòng)作發(fā)生的時(shí)候，信號(hào)允許特定的發(fā)送者去提醒一些接受者。
| 123456789101112131415161718192021 | Model signals????pre_init??????????????????? # django的model執(zhí)行其構(gòu)造方法前，自動(dòng)觸發(fā)????post_init?????????????????? # django的model執(zhí)行其構(gòu)造方法后，自動(dòng)觸發(fā)????pre_save??????????????????? # django的model對(duì)象保存前，自動(dòng)觸發(fā)????post_save?????????????????? # django的model對(duì)象保存后，自動(dòng)觸發(fā)????pre_delete????????????????? # django的model對(duì)象刪除前，自動(dòng)觸發(fā)????post_delete???????????????? # django的model對(duì)象刪除后，自動(dòng)觸發(fā)????m2m_changed???????????????? # django的model中使用m2m字段操作第三張表（add,remove,clear）前后，自動(dòng)觸發(fā)????class_prepared????????????? # 程序啟動(dòng)時(shí)，檢測(cè)已注冊(cè)的app中modal類，對(duì)于每一個(gè)類，自動(dòng)觸發(fā)Management signals????pre_migrate???????????????? # 執(zhí)行migrate命令前，自動(dòng)觸發(fā)????post_migrate??????????????? # 執(zhí)行migrate命令后，自動(dòng)觸發(fā)Request/response signals????request_started???????????? # 請(qǐng)求到來前，自動(dòng)觸發(fā)????request_finished??????????? # 請(qǐng)求結(jié)束后，自動(dòng)觸發(fā)????got_request_exception?????? # 請(qǐng)求異常后，自動(dòng)觸發(fā)Test signals????setting_changed???????????? # 使用test測(cè)試修改配置文件時(shí)，自動(dòng)觸發(fā)????template_rendered?????????? # 使用test測(cè)試渲染模板時(shí)，自動(dòng)觸發(fā)Database Wrappers????connection_created????????? # 創(chuàng)建數(shù)據(jù)庫連接時(shí)，自動(dòng)觸發(fā) |
對(duì)于Django內(nèi)置的信號(hào)，僅需注冊(cè)指定信號(hào)，當(dāng)程序執(zhí)行相應(yīng)操作時(shí)，自動(dòng)觸發(fā)注冊(cè)函數(shù)：
注冊(cè)信號(hào)，寫入與project同名的文件夾下的_init_.py文件中，也是換數(shù)據(jù)庫引擎的地方。
from django.core.signals import request_finished from django.core.signals import request_started from django.core.signals import got_request_exception from django.db.models.signals import class_prepared from django.db.models.signals import pre_init, post_init from django.db.models.signals import pre_save, post_save from django.db.models.signals import pre_delete, post_delete from django.db.models.signals import m2m_changed from django.db.models.signals import pre_migrate, post_migrate from django.test.signals import setting_changed from django.test.signals import template_rendered from django.db.backends.signals import connection_created def callback(sender, **kwargs): print("xxoo_callback") print(sender,kwargs) xxoo.connect(callback) # xxoo指上述導(dǎo)入的內(nèi)容View Codedef my_callback(sender, **kwargs): print("Request finished!")# 方法一：from django.core.signals import request_finishedrequest_finished.connect(my_callback)# 方法二：from django.core.signals import request_finishedfrom django.dispatch import receiver@receiver(request_finished)def my_callback(sender, **kwargs): print("Request finished!")示例
from django.db.models.signals import pre_savefrom django.dispatch import receiverfrom myapp.models import MyModel@receiver(pre_save, sender=MyModel)def my_handler(sender, **kwargs): ...指定發(fā)送者
a. 定義信號(hào)
在某py文件中定義信號(hào)。
?| 12 | import django.dispatchpizza_done = django.dispatch.Signal(providing_args=["toppings", "size"]) |
b. 注冊(cè)信號(hào)
在_init_.py 中注冊(cè)信號(hào)
?| 12345 | def callback(sender, **kwargs):????print("callback")????print(sender,kwargs)?pizza_done.connect(callback) |
c. 觸發(fā)信號(hào)
?| 123 | from 路徑 import pizza_done?pizza_done.send(sender='seven',toppings=123, size=456) |
由于內(nèi)置信號(hào)的觸發(fā)者已經(jīng)集成到Django中，所以其會(huì)自動(dòng)調(diào)用，而對(duì)于自定義信號(hào)則需要開發(fā)者在任意位置觸發(fā)。
更多：猛擊這里
關(guān)于Django中的序列化主要應(yīng)用在將數(shù)據(jù)庫中檢索的數(shù)據(jù)返回給客戶端用戶，特別的Ajax請(qǐng)求一般返回的為Json格式。
1、serializers
?| 12345 | from django.core import serializers?ret = models.BookType.objects.all()?data = serializers.serialize("json", ret) |
2、json.dumps
?| 12345678 | import json?#ret = models.BookType.objects.all().values('caption')ret = models.BookType.objects.all().values_list('caption')?ret=list(ret)?result = json.dumps(ret) |
由于json.dumps時(shí)無法處理datetime日期，所以可以通過自定義處理器來做擴(kuò)展，如：
View Code?| 1234567891011121314151617 | import json? from datetime import date? from datetime import datetime? ???class JsonCustomEncoder(json.JSONEncoder):? ????????def default(self, field):? ?????????????if isinstance(field, datetime):? ????????????return o.strftime('%Y-%m-%d %H:%M:%S')? ????????elif isinstance(field, date):? ????????????return o.strftime('%Y-%m-%d')? ????????else:? ????????????return json.JSONEncoder.default(self, field)? ??????# ds = json.dumps(d, cls=JsonCustomEncoder)? |
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