using System;
using System.Collections.Generic;
namespace DoFactory.GangOfFour.Command.RealWorld
{
/// <summary>
/// MainApp startup class for Real-World
/// Command Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
static void Main()
{
// Create user and let her compute
User user = new User();
// User presses calculator buttons
user.Compute('+', 100);
user.Compute('-', 50);
user.Compute('*', 10);
user.Compute('/', 2);
// Undo 4 commands
user.Undo(4);
// Redo 3 commands
user.Redo(3);
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// The 'Command' abstract class
/// </summary>
abstract class Command
{
public abstract void Execute();
public abstract void UnExecute();
}
/// <summary>
/// The 'ConcreteCommand' class
/// </summary>
class CalculatorCommand : Command
{
private char _operator;
private int _operand;
private Calculator _calculator;
// Constructor
public CalculatorCommand(Calculator calculator,
char @operator, int operand)
{
this._calculator = calculator;
this._operator = @operator;
this._operand = operand;
}
// Gets operator
public char Operator
{
set { _operator = value; }
}
// Get operand
public int Operand
{
set { _operand = value; }
}
// Execute new command
public override void Execute()
{
_calculator.Operation(_operator, _operand);
}
// Unexecute last command
public override void UnExecute()
{
_calculator.Operation(Undo(_operator), _operand);
}
// Returns opposite operator for given operator
private char Undo(char @operator)
{
switch (@operator)
{
case '+': return '-';
case '-': return '+';
case '*': return '/';
case '/': return '*';
default: throw new
ArgumentException("@operator");
}
}
}
/// <summary>
/// The 'Receiver' class
/// </summary>
class Calculator
{
private int _curr = 0;
public void Operation(char @operator, int operand)
{
switch (@operator)
{
case '+': _curr += operand; break;
case '-': _curr -= operand; break;
case '*': _curr *= operand; break;
case '/': _curr /= operand; break;
}
Console.WriteLine(
"Current value = {0,3} (following {1} {2})",
_curr, @operator, operand);
}
}
/// <summary>
/// The 'Invoker' class
/// </summary>
class User
{
// Initializers
private Calculator _calculator = new Calculator();
private List<Command> _commands = new List<Command>();
private int _current = 0;
public void Redo(int levels)
{
Console.WriteLine("\n---- Redo {0} levels ", levels);
// Perform redo operations
for (int i = 0; i < levels; i++)
{
if (_current < _commands.Count - 1)
{
Command command = _commands[_current++];
command.Execute();
}
}
}
public void Undo(int levels)
{
Console.WriteLine("\n---- Undo {0} levels ", levels);
// Perform undo operations
for (int i = 0; i < levels; i++)
{
if (_current > 0)
{
Command command = _commands[--_current] as Command;
command.UnExecute();
}
}
}
public void Compute(char @operator, int operand)
{
// Create command operation and execute it
Command command = new CalculatorCommand(
_calculator, @operator, operand);
command.Execute();
// Add command to undo list
_commands.Add(command);
_current++;
}
}
}