知識點

1. 概念
2. 如何監聽信號
3. Django內置信號
4. 自定義信號
5. 使用Django內置信號

概念

Django 提供一個“信號分發器”，允許解耦的應用在框架的其它地方發生操作時會被通知到。
也就是說在特定事件發生時，可以發送一個信號去通知注冊了這個信號的一個或者多個回調，在回調里進行邏輯處理。

如何監聽信號

擁有一個Signal實例
信號回調
將信號回調綁定到Signal實例
在特定事件中Signal發送信號

Django內置信號

django.db.models.signals.pre_save & post_save?在模型 save()方法調用之前或之后發送。
django.db.models.signals.pre_delete & post_delete?在模型delete()方法或查詢集的delete() 方法調用之前或之后發送。
django.core.signals.request_started & request_finished?Django建立或關閉HTTP 請求時發送。

參考文檔

代碼地址：Spareibs的Github

實驗操作

自定義信號

注冊信號

【signal.py】

from django.dispatch import Signal, receiver

signalAllen = Signal(providing_args=['allen'])

@receiver(signalAllen)
def signal_callback(sender, **kwargs):
    print(sender, kwargs)
    print('signal_callback called')

# 注冊，或者使用裝飾器注冊
# signalAllen.connect(signal_callback)

# 可以定義多個
@receiver(signalAllen)
def signal_callback1(sender, **kwargs):
    print(sender, kwargs)
    print('signal_callback1 called')

【urls.py】

from django.conf.urls import url
from . import views

urlpatterns = [
    url(r'^$', view=views.index),
]

【views.py】

from . import signals
# Create your views here.

def index(request):
    signals.signalAllen.send(sender=None, allen='test')
    return render(request, template_name='index.html')

刪除信號

【urls.py】

from django.conf.urls import url
from . import views

urlpatterns = [
    url(r'^disconnect/$', view=views.disconnect_signal),
]

【views.py】

def disconnect_signal(request):
    signals.signalAllen.disconnect(signals.signal_callback)
    return render(request, template_name='index.html')

Django 內置信號

簡單使用

【views.py】

from django.shortcuts import render
from .models import Poem, Task
# Create your views here.

def modify(request):
    poem = Poem.objects.get(pk=1)
    poem.title = '1'
    # 會發送兩個信號pre_save和post_save
    poem.save()

    task = Task.objects.get(pk=1)
    task.name = '1'
    task.save()

    return render(request, template_name='index.html')

【urls.py】

from django.conf.urls import url
from . import views

urlpatterns = [
    url(r'^modify/$', view=views.modify),
]

【singals.py】

from django.db.models.signals import pre_save, post_save

@receiver(pre_save)
def pre_save_callback(sender, **kwargs):
    print('pre_save_callback')


@receiver(post_save)
def post_save_callback(sender, **kwargs):
    print('post_save_callback')

指定信號

【views.py】

from django.shortcuts import render
from .models import Poem, Task
# Create your views here.

def modify(request):
    poem = Poem.objects.get(pk=1)
    poem.title = '1'
    # 會發送兩個信號pre_save和post_save
    poem.save()

    task = Task.objects.get(pk=1)
    task.name = '1'
    task.save()

    return render(request, template_name='index.html')

【urls.py】

from django.conf.urls import url
from . import views

urlpatterns = [
    url(r'^modify/$', view=views.modify),
]

【singals.py】

from django.db.models.signals import pre_save, post_save
from .models import Poem, Task

@receiver(pre_save, sender=Poem)
def pre_save_callback(sender, **kwargs):
    print('pre_save_callback', sender, kwargs)


@receiver(post_save, sender=Task)
def post_save_callback(sender, **kwargs):
    print('post_save_callback', sender, kwargs)