Source Code for Module pypat.behavioral.command

 1  from abc import ABCMeta, abstractmethod 
 2   
 3   
 4 -class Receiver(object, metaclass=ABCMeta): 
 5      """ 
 6      Abstract receiver class as part of the Command pattern. 
 7   
 8      - External Usage documentation: U{https://github.com/tylerlaberge/PyPatterns/wiki/Behavioral-Pattern-Usage} 
 9      - External Command Pattern documentation: U{https://en.wikipedia.org/wiki/Command_pattern} 
10      """ 
11 -    def action(self, name, *args, **kwargs): 
12          """ 
13          Delegates which method to be called for a desired action. 
14   
15          @param name: The name of the action to execute. 
16          @type name: str 
17          @param args: Any arguments for the action. 
18          @param kwargs: Any keyword arguments for the action. 
19          """ 
20          try: 
21              return getattr(self, name)(*args, **kwargs) 
22          except AttributeError: 
23              raise AttributeError('Invalid Action.') 
24   
25   
26 -class Command(object, metaclass=ABCMeta): 
27      """ 
28      Abstract Command class as part of the Command pattern. 
29   
30      - External Usage documentation: U{https://github.com/tylerlaberge/PyPatterns/wiki/Behavioral-Pattern-Usage} 
31      - External Command Pattern documentation: U{https://en.wikipedia.org/wiki/Command_pattern} 
32      """ 
33 -    def __init__(self, receiver): 
34          """ 
35          Initialize a new command instance. 
36   
37          @param receiver: The receiver for this command to use. 
38          @type receiver: Receiver 
39          """ 
40          self._receiver = receiver 
41   
42      @abstractmethod 
43 -    def execute(self): 
44          """ 
45          Abstract method for executing an action. 
46          """ 
47          pass 
48   
49      @abstractmethod 
50 -    def unexecute(self): 
51          """ 
52          Abstract method for unexecuting an action. 
53          """ 
54          pass 
55   
56   
57 -class Invoker(object, metaclass=ABCMeta): 
58      """ 
59      Abstract Invoker class as part of the Command pattern. 
60   
61      - External Usage documentation: U{https://github.com/tylerlaberge/PyPatterns/wiki/Behavioral-Pattern-Usage} 
62      - External Command Pattern documentation: U{https://en.wikipedia.org/wiki/Command_pattern} 
63      """ 
64 -    def __init__(self, valid_commands): 
65          """ 
66          Initialize a new Invoker instance. 
67   
68          @param valid_commands: A list of command classes this invoker can handle. 
69          """ 
70          self._history = [] 
71          self._valid_commands = valid_commands 
72   
73 -    def execute(self, command): 
74          """ 
75          Execute a command. 
76   
77          @param command: A command for the invoker to execute. 
78          @type command: Command 
79          """ 
80          if command.__class__ not in self._valid_commands: 
81              raise AttributeError('Invalid Command') 
82          else: 
83              self._history.append(command) 
84              return command.execute() 
85   
86 -    def undo(self): 
87          """ 
88          Undo the last command. 
89          """ 
90          return self._history.pop().unexecute() 
91