命令模式

如何在应用中实现撤销功能。
推荐哪个设计模式来实现撤销，那就是命令模式

命令模式帮助我们讲一个操作（撤销、重复、复制、粘贴）封装成一个对象。
    我们并不需要直接执行一个命令，命令可以按照希望执行
    调用命令的对象与指导如何执行命令的对象解耦。调用者无需知道命令的任何实现细节
    如果有意义，可以把多个命令组织起来，这样调用者能够按顺序执行他们。例如，在实现一个多层撤销命令时，这是很有用的。

 

 

 

 

import os

verbose = True


class RenameFile:

    def __init__(self, path_src, path_dest):
        self.src, self.dest = path_src, path_dest

    def execute(self):
        if verbose:
            print("[renaming '{}' to '{}']".format(self.src, self.dest))
        os.rename(self.src, self.dest)

    def undo(self):
        if verbose:
            print("[renaming '{}' back to '{}']".format(self.dest, self.src))
        os.rename(self.dest, self.src)


class CreateFile:

    def __init__(self, path, txt='hello world\n'):
        self.path, self.txt = path, txt

    def execute(self):
        if verbose:
            print("[creating file '{}']".format(self.path))
        with open(self.path, mode='w', encoding='utf-8') as out_file:
            out_file.write(self.txt)

    def undo(self):
        delete_file(self.path)


class ReadFile:

    def __init__(self, path):
        self.path = path

    def execute(self):
        if verbose:
            print("[reading file '{}']".format(self.path))
        with open(self.path, mode='r', encoding='utf-8') as in_file:
            print(in_file.read(), end='')


def delete_file(path):
    if verbose:
        print("deleting file '{}'".format(path))
    os.remove(path)


def main():
    orig_name, new_name = 'file1', 'file2'

    commands = []
    for cmd in CreateFile(orig_name), ReadFile(orig_name), RenameFile(orig_name, new_name):
        commands.append(cmd)

    [c.execute() for c in commands]

    answer = input('reverse the executed commands? [y/n] ')

    if answer not in 'yY':
        print("the result is {}".format(new_name))
        exit()

    for c in reversed(commands):
        try:
            c.undo()
        except AttributeError as e:
            pass


if __name__ == '__main__':
    main()