Command Pattern
Description:
» The Command pattern creates distance between the client that requests an operation and the object that can perform it.Use When:
» You want to specify, queue, and execute commands at different times;» You want to support an Undo function for commands;
» You want to support auditing and logging of all changes via commands.
//Define the Pattern Interface and Command Objects.
//Define the ICommand interface to be used as the "blueprint" for the main application classes.
//This interface defines the Execute, Redo and Undo methods and has a local instance of type Receiver.
//The Receiver class (object) represents the class that will have the code logic to actually execute the required command, and this is where all the work will be done.
public interface ICommand
{
Receiver Receiver { get; set; }
void Execute();
void Redo();
void Undo();
}
//The Paste class (object) represents a unique command that needs to be actioned.
//This class inherits from the ICommand object, and therefore implements the Execute, Redo and Undo methods and has a local variable of type Receiver defined.
public class Paste : ICommand
{
Receiver Receiver { get; set; }
public void Execute();
{
Receiver.Paste();
}
public void Redo()
{
Receiver.Paste();
}
public void Undo()
{
Receiver.Restore();
}
}
//The Print class (object) represents another unique command that needs to be actioned.
//And as before, this class inherits from the ICommand object, and therefore implements the Execute, Redo and Undo methods and has a local variable of type Receiver defined.
//The difference here, between the Paste command and the Print command, is that the Print command does not have a logical Undo process. So nothing needs doing when this method is called.
public class Print : ICommand
{
Receiver Receiver { get; set; }
public void Execute();
{
Receiver.Print();
}
public void Redo()
{
Receiver.Print();
}
public void Undo()
{
Console.WriteLine("Cannot undo a Print!\n");
}
}
//Define the ICommand interface to be used as the "blueprint" for the main application classes.
//This interface defines the Execute, Redo and Undo methods and has a local instance of type Receiver.
//The Receiver class (object) represents the class that will have the code logic to actually execute the required command, and this is where all the work will be done.
public interface ICommand
{
Receiver Receiver { get; set; }
void Execute();
void Redo();
void Undo();
}
//The Paste class (object) represents a unique command that needs to be actioned.
//This class inherits from the ICommand object, and therefore implements the Execute, Redo and Undo methods and has a local variable of type Receiver defined.
public class Paste : ICommand
{
Receiver Receiver { get; set; }
public void Execute();
{
Receiver.Paste();
}
public void Redo()
{
Receiver.Paste();
}
public void Undo()
{
Receiver.Restore();
}
}
//The Print class (object) represents another unique command that needs to be actioned.
//And as before, this class inherits from the ICommand object, and therefore implements the Execute, Redo and Undo methods and has a local variable of type Receiver defined.
//The difference here, between the Paste command and the Print command, is that the Print command does not have a logical Undo process. So nothing needs doing when this method is called.
public class Print : ICommand
{
Receiver Receiver { get; set; }
public void Execute();
{
Receiver.Print();
}
public void Redo()
{
Receiver.Print();
}
public void Undo()
{
Console.WriteLine("Cannot undo a Print!\n");
}
}
//Define the Pattern Interface and Command Objects.
//Define the ICommand interface to be used as the "blueprint" for the main application classes.
//This interface defines the Execute, Redo and Undo methods and has a local instance of type Receiver.
//The Receiver class (object) represents the class that will have the code logic to actually execute the required command, and this is where all the work will be done.
public interface ICommand
{
Receiver Receiver { get; set; }
void Execute();
void Redo();
void Undo();
}
//The Paste class (object) represents a unique command that needs to be actioned.
//This class inherits from the ICommand object, and therefore implements the Execute, Redo and Undo methods and has a local variable of type Receiver defined.
public class Paste : ICommand
{
Receiver Receiver { get; set; }
public void Execute();
{
Receiver.Paste();
}
public void Redo()
{
Receiver.Paste();
}
public void Undo()
{
Receiver.Restore();
}
}
//The Print class (object) represents another unique command that needs to be actioned.
//And as before, this class inherits from the ICommand object, and therefore implements the Execute, Redo and Undo methods and has a local variable of type Receiver defined.
//The difference here, between the Paste command and the Print command, is that the Print command does not have a logical Undo process. So nothing needs doing when this method is called.
public class Print : ICommand
{
Receiver Receiver { get; set; }
public void Execute();
{
Receiver.Print();
}
public void Redo()
{
Receiver.Print();
}
public void Undo()
{
Console.WriteLine("Cannot undo a Print!\n");
}
}
//Define the ICommand interface to be used as the "blueprint" for the main application classes.
//This interface defines the Execute, Redo and Undo methods and has a local instance of type Receiver.
//The Receiver class (object) represents the class that will have the code logic to actually execute the required command, and this is where all the work will be done.
public interface ICommand
{
Receiver Receiver { get; set; }
void Execute();
void Redo();
void Undo();
}
//The Paste class (object) represents a unique command that needs to be actioned.
//This class inherits from the ICommand object, and therefore implements the Execute, Redo and Undo methods and has a local variable of type Receiver defined.
public class Paste : ICommand
{
Receiver Receiver { get; set; }
public void Execute();
{
Receiver.Paste();
}
public void Redo()
{
Receiver.Paste();
}
public void Undo()
{
Receiver.Restore();
}
}
//The Print class (object) represents another unique command that needs to be actioned.
//And as before, this class inherits from the ICommand object, and therefore implements the Execute, Redo and Undo methods and has a local variable of type Receiver defined.
//The difference here, between the Paste command and the Print command, is that the Print command does not have a logical Undo process. So nothing needs doing when this method is called.
public class Print : ICommand
{
Receiver Receiver { get; set; }
public void Execute();
{
Receiver.Print();
}
public void Redo()
{
Receiver.Print();
}
public void Undo()
{
Console.WriteLine("Cannot undo a Print!\n");
}
}