Memento Pattern
Description:
» The Memento pattern is used to to capture an object's internal state and save it externally so that it can be restored later;» The Memento pattern is used extensively in scientific computing to save the state of long-running computations, in computer games to save the state of play over a matter of hours or days and in graphics toolkits to preserve the state of a display while objects are being moved around.
Use When:
» An object's state must be saved to be restored later;» It is undesirable to expose the state directly.
//Define the Memento Object.
//Define the Memento class (object) which is responsible for implementing the functionality to save and restore application state.
//The application data is saved (serialized) into a binary format.
[Serializable]
public class Memento
{
private MemoryStream _stream = new MemoryStream();
private BinaryFormatter _formatter = new BinaryFormatter();
public object Restore()
{
_stream.Seek(0, SeekOrigin.Begin);
object o = _formatter.Deserialize(_stream);
_stream.Close();
return (o);
}
public Memento Save(object o)
{
_formatter.Serialize(_stream, o);
return this;
}
}
//Define the Memento class (object) which is responsible for implementing the functionality to save and restore application state.
//The application data is saved (serialized) into a binary format.
[Serializable]
public class Memento
{
private MemoryStream _stream = new MemoryStream();
private BinaryFormatter _formatter = new BinaryFormatter();
public object Restore()
{
_stream.Seek(0, SeekOrigin.Begin);
object o = _formatter.Deserialize(_stream);
_stream.Close();
return (o);
}
public Memento Save(object o)
{
_formatter.Serialize(_stream, o);
return this;
}
}
//Define the Caretaker Object.
//The Caretaker class (object) stores an instance of the Memento class (object).
public class Caretaker
{
public Memento Memento { get; set; }
}
//The Caretaker class (object) stores an instance of the Memento class (object).
public class Caretaker
{
public Memento Memento { get; set; }
}