设计模式之备忘录模式
结构
说明
Without violating encapsulation, capture and externalize an object’s internal state allowing the object to be restored to this state later.
在不破坏封装的条件下，将一个对象的状态捉住，并外部化，存储起来，从而可以在将来合适的时候把这个对象还原到存储起来的状态。
适用条件
需要保存对象在某一时刻的状态， 并在以后需要将对象恢复到这个状态； 同时又不希望暴露对象的实现细节， 破坏对象的封装性， 这是需要使用备忘录模式。
实现
public class Originator {
private string _state;
public void SetState(string state) {
Console.WriteLine("Originator: setting momento to {0}", state);
this._state = state;
}
public Momento SaveToMomento() {
Console.WriteLine("Originator: saving to momento...");
return new Originator.Momento(this._state);
}
public void RestoreFromMomento(Momento momento) {
this._state = momento.State;
Console.WriteLine("Originator: resotring from momento {0}", this._state);
}
public class Momento {
private readonly string _state;
internal Momento(string state) {
this._state = state;
}
public string State {
get {
return this._state;
}
}
}
}
class CareTaker {
static void Main(string[] args) {
IList<Originator.Momento> savedStates = new List<Originator.Momento>();
var originator = new Originator();
originator.SetState("State1");
originator.SetState("State2");
savedStates.Add(originator.SaveToMomento());
originator.SetState("State3");
savedStates.Add(originator.SaveToMomento());
originator.SetState("State4");
originator.RestoreFromMomento(savedStates[0]);
Console.ReadKey();
}
}