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from abc import ABC, abstractmethod |
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import copy |
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from typing import List |
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__all__ = ['Command', 'Invoker', 'CommandHistory'] |
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class CommandInterface(ABC): |
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"""A class implementing this interface can act as a standalone command, encapsulating all logic and data needed.""" |
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@abstractmethod |
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def execute(self) -> None: |
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"""Call this method to execute the command. |
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""" |
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raise NotImplementedError |
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class AbstractCommand(CommandInterface, ABC): |
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"""An abstract implementation of the Command Interface. The assumption is that the command involves a 'reveiver' object |
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(of arbitrary type) acting as an 'oracle' on the application. |
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Args: |
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receiver (object): an object that is actually executing/receiving the command; usually holds the callback function/code |
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""" |
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def __init__(self, receiver): |
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self._receiver = receiver |
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class BaseCommand(AbstractCommand): |
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"""A basic implementation of the Abstract Command. The assumption is that the command involves calling a method of the reveiver |
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using the user-provided function arguments. Use the optional args to provide the receiver's method runtime arguments. |
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Args: |
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receiver (object): an object that is actually executing/receiving the command; usually holds the callback function/code |
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method (str): the name of the receiver's method to call (it has to be callable and to exist on the receiver) |
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""" |
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def __init__(self, receiver, method: str, *args): |
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super().__init__(receiver) |
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self._method = method |
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self._args = [_ for _ in args] # this is a list that can be minimally be [] |
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def append_arg(self, *args): |
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self._args.extend([_ for _ in args]) |
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@property |
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def args(self): |
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return self._args |
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@args.setter |
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def args(self, args_list): |
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self._args = args_list |
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def execute(self) -> None: |
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getattr(self._receiver, self._method)(*self._args) |
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class Command(BaseCommand): |
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"""A BaseCommand acting as a prototype. The receiver is copied explicitly in a shallow way. The rest are |
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assumed to be performance invariant (eg it is not expensive to copy the 'method' attribute, which is a string) and are handled automatically. |
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""" |
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def __copy__(self): |
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_ = Command(copy.copy(self._receiver), self._method) |
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_.append_arg(*self._args) |
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return _ |
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class CommandHistory: |
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"""The global command history is just a stack; supports 'push' and 'pop' methods.""" |
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def __init__(self): |
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self._history = [] |
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def push(self, c: Command): |
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self._history.append(c) |
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def pop(self) -> Command: |
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return self._history.pop(0) |
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class Invoker: |
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"""A class that simply executes a command and pushes it into its internal command history stack. |
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Args: |
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history (CommandHistory): the command history object which acts as a stack |
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""" |
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def __init__(self, history: CommandHistory): |
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self.history = history |
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def execute_command(self, command: Command): |
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if command.execute(): |
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self.history.push(command) |
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if __name__ == '__main__': |
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class A: |
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def a(self, x): |
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res = x + 1 |
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print(res) |
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a = A() |
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invoker = Invoker(CommandHistory()) |
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cmd1 = Command(a, 'a', 2) |
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invoker.execute_command(cmd1) |
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cmd2 = copy.copy(cmd1) |
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cmd2.args = [12] |
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invoker.execute_command(cmd2) |
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invoker.execute_command(cmd1) |
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del cmd2 |
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invoker.execute_command(cmd1) |
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boromir674 /
so-magic
