what design pattern for pre-do in class function

Question

My class function alway need do something before like this (Python):

class X:
 def f1():
  #### 
  if check() == False: 
   return;
  set_A()
  ####
  f1_do_something

 def f2():
  #### 
  if check() == False: 
   return;
  set_A()
  ####

  f2_do_something

And I want to :

class X:
 def f1():
  # auto check-return-set_A()
  f1_do_something

 def f2():
  # auto check-return-set_A() 
  f2_do_something

I've read about design patterns and I do not know how to apply design patterns in this case. If there is no any suitable design patterns, are there any other solution to this problem?

score 5 · Accepted Answer · edited May 23 '17 at 12:12

5

You could use a decorator:

#!/usr/bin/env python

def check(f, *args, **kwargs):
    def inner(*args, **kwargs):
        print 'checking...'
        return f(*args, **kwargs)
    return inner

class Example(object):

    @check
    def hello(self):
        print 'inside hello'

    @check
    def hi(self):
        print 'inside hi'

if __name__ == '__main__':
    example = Example()
    example.hello()
    example.hi()

This snippet would print:

checking...
inside hello
checking...
inside hi

If you go this route, please check out functools.wrap, which makes decorators aware of the original function's name and documentation.

edited May 23 '17 at 12:12

Community

1
1

answered Jan 11 '12 at 06:30

miku

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I suggest decorate your decorator with the function decorator decorator: http://docs.python.org/library/functools.html#functools.wraps – Anders Waldenborg Jan 11 '12 at 06:35
@AndersWaldenborg, thanks, added a note to my post. I haven't added it directly in the code, because I wanted to keep it as simple as possible to focus on the idea. – miku Jan 11 '12 at 06:38

what design pattern for pre-do in class function

1 Answers1