Python: Command Pattern

GeovinDuCommand.py

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# 命令模式 Command  Pattern  GeovinDuCommand.py   # Web Browser: class WebBrowser(object):     def __init__(self):         self.bookmarks = []         self.currentUrl = None       def Navigate(self, url):         self.currentUrl = url       def BookmarkCurrentPage(self):         valid = self.currentUrl is not None         contains = self.currentUrl in self.bookmarks         if valid and not contains:             self.bookmarks.append(self.currentUrl)       def RemoveBookmark(self, url):         self.bookmarks.remove(url)       def PrintBookmarks(self):         print("书签:")         for i in self.bookmarks:             print("\t" + str(i))   # AddBookmarkCommand: class AddBookmarkCommand(object):    def __init__(self, webBrowser):        self.webBrowser = webBrowser        self.url = None      def Execute(self):        self.url = self.webBrowser.currentUrl        self.webBrowser.BookmarkCurrentPage()      def Undo(self):        self.webBrowser.RemoveBookmark(self.url)      def Redo(self):        self.Execute()   # Bookmarker: class Bookmarker(object):    def __init__(self, webBrowser):        self.webBrowser = webBrowser        self.undoStack = []        self.redoStack = []      def BookmarkCurrentPage(self):        command = AddBookmarkCommand(self.webBrowser)        self.undoStack.append(command)        self.redoStack = []          command.Execute()      def UndoBookmark(self):        if len(self.undoStack) != 0:            command = self.undoStack.pop()            self.redoStack.append(command)              command.Undo()      def RedoBookmark(self):        if len(self.redoStack) != 0:            command = self.redoStack.pop()            self.undoStack.append(command)              command.Redo()   # 2 geovindu class data:     _data = 0       def __init__(self, value=0) -> None:         data._data += value         def add(self):         pass         def subtract(self):         pass       def __str__(self) -> str:         return f"现值: {data._data}"     class Addition(data):     def __init__(self, value=0) -> None:         super().__init__(value)       def add(self, value):         data._data += value         print("正在执行加法操作...")       def __str__(self) -> str:         return super().__str__()     class Subtraction(data):     def __init__(self, value=0) -> None:         super().__init__(value)       def subtract(self, value):         data._data -= value         print("正在进行减法运算...")       def __str__(self) -> str:         return super().__str__()   class Command():       def execute(self):         pass         def undo(self):         pass   class AdditionCommand(Command):     def __init__(self, obj, value):         self.obj = obj         self.value = value       def execute(self):         self.obj.add(self.value)       def undo(self, commandObj):         commandObj.set_command(SubtractionCommand(Subtraction(), self.value))         commandObj.invoke()     class SubtractionCommand(Command):     def __init__(self, obj, value):         self.obj = obj         self.value = value       def execute(self):         self.obj.subtract(self.value)       def undo(self, commandObj):         commandObj.set_command(AdditionCommand(Addition(), self.value))         commandObj.invoke()     class ActionInvoker:     def __init__(self, command):         self.command = command       def set_command(self, command):         self.command = command       def invoke(self):         self.command.execute()       def undo(self):         print("[!UNDO] ", end="")         self.command.undo(self)

　　

main.py 调用

 

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# 命令模式 Command  Pattern   memeSurfer = GeovinDuCommand.WebBrowser()   bookmarker = GeovinDuCommand.Bookmarker(memeSurfer)   memeSurfer.Navigate("geovindu.gov") bookmarker.BookmarkCurrentPage()   memeSurfer.PrintBookmarks()   memeSurfer.Navigate("dusystem.com") bookmarker.BookmarkCurrentPage()   memeSurfer.PrintBookmarks()   bookmarker.UndoBookmark()   memeSurfer.PrintBookmarks()   bookmarker.RedoBookmark()   memeSurfer.PrintBookmarks() print("\n") obj = GeovinDuCommand.data(100) print(obj) command_addition = GeovinDuCommand.AdditionCommand(GeovinDuCommand.Addition(), 10) # concrete command command_subtraction = GeovinDuCommand.SubtractionCommand(GeovinDuCommand.Subtraction(), 10) # concrete command   action_invoker = GeovinDuCommand.ActionInvoker(command_addition); # invoker action_invoker.invoke() print(obj)   action_invoker.set_command(command_subtraction) action_invoker.invoke() print(obj)   action_invoker.undo() print(obj) action_invoker.undo() print(obj)

　　

输出：

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书签:     geovindu.gov 书签:     geovindu.gov     dusystem.com 书签:     geovindu.gov 书签:     geovindu.gov     dusystem.com     现值: 100 正在执行加法操作... 现值: 110 正在进行减法运算... 现值: 100 [!UNDO] 正在执行加法操作... 现值: 110 [!UNDO] 正在进行减法运算... 现值: 100   Process finished with exit code 0