Dp Command

In this tutorial, you'll learn about How to Fix Command Errors. We cover key concepts, practical examples, and best practices.

Fix command errors when operations hardcoded in UI layer instead of encapsulated commands.

Quick Fix

Wrong

class Button:
    def __init__(self,label): self.label=label
    def click(self):
        if self.label=='Save':
            print('Saving...')
        elif self.label=='Print':
            print('Printing...')

Button knows about application logic. Adding new action requires modifying Button class.

Right

from abc import ABC,abstractmethod
class Command(ABC):
    @abstractmethod
    def execute(self): pass
class SaveCommand(Command):
    def execute(self): print('Saving...')
class PrintCommand(Command):
    def execute(self): print('Printing...')
class Button:
    def __init__(self,label,cmd):
        self.label=label; self.cmd=cmd
    def click(self): self.cmd.execute()
Button('Save',SaveCommand()).click()

Button doesn't know what happens. Command object encapsulates action. Undo/redo possible.

Prevention

Command pattern encapsulates request as object. Parameterize, queue, log, undo operations.

DodaTech Tools

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FAQ