Python责任链模式
Python责任链模式详细操作教程
责任链模式用于在软件中实现松散耦合，其中来自客户端的指定请求通过其中包含的对象链传递。它有助于构建对象链。该请求从一端进入，从一个对象移动到另一对象。
此模式允许对象发送命令而无需知道哪个对象将处理请求。
如何实施责任链模式？
我们现在将了解如何实施责任链模式。
# Filename : example.py
# Copyright : 2020 By Lidihuo
# Author by : www.lidihuo.com
# Date : 2020-08-22
class ReportFormat(object):
PDF = 0
TEXT = 1
class Report(object):
def __init__(self, format_):
self.title = 'Monthly report'
self.text = ['Things are going', 'really, really well.']
self.format_ = format_
class Handler(object):
def __init__(self):
self.nextHandler = None
def handle(self, request):
self.nextHandler.handle(request)
class PDFHandler(Handler):
def handle(self, request):
if request.format_ == ReportFormat.PDF:
self.output_report(request.title, request.text)
else:
super(PDFHandler, self).handle(request)
def output_report(self, title, text):
print('')
print(' ')
print(' %s' % title)
print(' ')
print(' ')
for line in text:
print(' %s' % line)
print(' ')
print(' ')
class TextHandler(Handler):
def handle(self, request):
if request.format_ == ReportFormat.TEXT:
self.output_report(request.title, request.text)
else:
super(TextHandler, self).handle(request)
def output_report(self, title, text):
print(5*'*' + title + 5*'*')
for line in text:
print(line)
class ErrorHandler(Handler):
def handle(self, request):
print("Invalid request")
if __name__ == '__main__':
report = Report(ReportFormat.TEXT)
pdf_handler = PDFHandler()
text_handler = TextHandler()
pdf_handler.nextHandler = text_handler
text_handler.nextHandler = ErrorHandler()
pdf_handler.handle(report)
输出
上面的程序生成以下输出-
Things are going
really, really well.
说明
上面的代码创建了每月任务的报告，并在其中通过每个功能发送命令。它需要两个处理程序– PDF和文本。一旦所需对象执行了每个功能，它将打印输出。
