Memento
?
Memento 提供了保存對(duì)象狀態(tài)的能力，似乎沒(méi)有什么好說(shuō)的。
1//?Memento
??2
??3//?Intent:?"Without?violating?encapsulation,?capture?and?externalize?an?
??4//?object's?internal?state?so?that?an?object?can?be?restored?to?this?
??5//?state?later."?
??6
??7//?For?further?information,?read?"Design?Patterns",?p283,?Gamma?et?al.,
??8//?Addison-Wesley,?ISBN:0-201-63361-2
??9
?10/**//*?Notes:
?11?*?We?often?have?client?code?that?wishes?to?record?the?current?state?of?an?
?12?*?object,?without?being?interested?in?the?actual?data?values?(this?is?
?13?*?needed?for?undo?and?checkpointing).?To?support?this?behavior,?we?can?have
?14?*?the?object?record?its?internal?data?in?a?helper?class?called?a?memento,?and
?15?*?the?client?code?can?treat?this?as?an?opaque?store?of?the?object's?state.?
?16?*?At?some?later?point,?the?client?can?pass?the?memento?back?into?the?object,?
?17?*?to?restore?it?to?the?previous?state.?
?18?*/
?19?
?20namespace?Memento_DesignPattern
?21{
?22????using?System;
?23
?24????class?Originator?
?25????{
?26????????private?double?manufacturer=0;
?27????????private?double?distributor?=?0;
?28????????private?double?retailer?=?0;
?29
?30????????public?void?MakeSale(double?purchasePrice)
?31????????{
?32????????????//?We?assume?sales?are?divided?equally?amount?the?three
?33????????????manufacturer?+=?purchasePrice?*?.40;
?34????????????distributor?+=?purchasePrice?*.3;
?35????????????retailer?+=?purchasePrice?*.3;
?36????????????//?Note:?to?avoid?rounding?errors?for?real?money?handling?
?37????????????//?apps,?we?should?be?using?decimal?integers
?38????????????//?(but?hey,?this?is?just?a?demo!)
?39????????}
?40
?41????????public?Memento?CreateMemento()
?42????????{
?43????????????return?(new?Memento(manufacturer,?distributor,?retailer));????????????
?44????????}
?45????????
?46????????public?void?SetMemento(Memento?m)
?47????????{
?48????????????manufacturer?=?m.A;
?49????????????distributor?=?m.B;
?50????????????retailer?=?m.C;
?51????????}????????
?52????}
?53
?54????class?Memento?
?55????{
?56????????private?double?iA;
?57????????private?double?iB;
?58????????private?double?iC;
?59
?60????????public?Memento(double?a,?double?b,?double?c)
?61????????{
?62????????????iA?=?a;
?63????????????iB?=?b;
?64????????????iC?=?c;
?65????????}
?66
?67????????public?double?A?
?68????????{
?69????????????get?
?70????????????{
?71????????????????return?iA;
?72????????????}
?73????????}
?74
?75????????public?double?B?
?76????????{
?77????????????get?
?78????????????{
?79????????????????return?iB;
?80????????????}
?81????????}
?82
?83????????public?double?C?
?84????????{
?85????????????get?
?86????????????{
?87????????????????return?iC;
?88????????????}
?89????????}
?90????}
?91
?92????class?caretaker?
?93????{
?94????????
?95????}
?96
?97????????/**////?<summary>
?98????///????Summary?description?for?Client.
?99????///?</summary>
100????public?class?Client
101????{
102????????public?static?int?Main(string[]?args)
103????????{??????????????
104????????????Originator?o?=?new?Originator();
105????????????
106????????????//?Assume?that?during?the?course?of?running?an?application?
107????????????//?we?we?set?various?data?in?the?originator
108????????????o.MakeSale(45.0);
109????????????o.MakeSale(60.0);
110
111????????????//?Now?we?wish?to?record?the?state?of?the?object
112????????????Memento?m?=?o.CreateMemento();
113
114????????????//?We?make?further?changes?to?the?object
115????????????o.MakeSale(60.0);
116????????????o.MakeSale(10.0);
117????????????o.MakeSale(320.0);
118
119????????????//?Then?we?decide?ot?change?our?minds,?and?revert?to?the?saved?state?(and?lose?the?changes?since?then)
120????????????o.SetMemento(m);
121
122????????????return?0;
123????????}
124????}
125}
126
127
“保存狀態(tài)”，似乎有點(diǎn)似曾相識(shí)，我們?cè)赟ingleton曾經(jīng)序列化保存過(guò)其狀態(tài)并回復(fù)。
序列化的話相當(dāng)于重新構(gòu)建對(duì)象，好處是程序結(jié)束后都可以保存狀態(tài)。顯然Memento是相對(duì)比較輕量級(jí)的解決方案，保存狀態(tài)類可以使用原型模式的Clone方法。也可以與Command模式共同使用為其提供Undo的狀態(tài)保存。
static?void?Main?(string[]?args)
??{
???Book?book?=?new?Book("Day?and?Night",?30.0f,?"Bruce");?
?
???using(FileStream?fs?=?new?FileStream(@"C:\book.dat",?FileMode.Create))
???{
????BinaryFormatter?formatter?=?new?BinaryFormatter();
????formatter.Serialize(fs,?book);
???}?
?
???book?=?null;?
?
???using(FileStream?fs?=?new?FileStream(@"C:\book.dat",?FileMode.Open))
???{
????BinaryFormatter?formatter?=?new?BinaryFormatter();
????book?=?(Book)formatter.Deserialize(fs);//在這里大家要注意咯,他的返回值是object
???}
??}?
?
XMLSerilizeExample1.?XML?serialization?serializes?only?the?public?fields?and?property?values?of?an?object?into?an?XML?stream?
2.?XML?serialization?does?not?include?type?information?
3.?XML?serialization?requires?a?default?constructor?to?be?declared?in?the?class?that?is?to?be?serialized?
4.?XML?serialization?requires?all?properties?that?are?to?be?serialized?as?read?write?properties.??Read?only?properties?are?not?serialized.?
[C#]?
using?System;
using?System.IO;
using?System.Text;
using?System.Xml;
using?System.Xml.Serialization;
//?This?is?the?class?that?will?be?serialized.
public?class?OrderedItem
{
???public?string?ItemName;
???public?string?Description;
???public?decimal?UnitPrice;
???public?int?Quantity;
???public?decimal?LineTotal;
???//?A?custom?method?used?to?calculate?price?per?item.
???public?void?Calculate()
???{
??????LineTotal?=?UnitPrice?*?Quantity;
???}
}
?
public?class?Test{
???public?static?void?Main()
???{
??????Test?t?=?new?Test();
??????//?Write?a?purchase?order.
??????t.SerializeObject("simple.xml");
??????t.DeserializeObject("simple.xml");
???}
?
???private?void?SerializeObject(string?filename)
???{
??????Console.WriteLine("Writing?With?XmlTextWriter");
?
??????XmlSerializer?serializer?=?
??????new?XmlSerializer(typeof(OrderedItem));
??????OrderedItem?i?=?new?OrderedItem();
??????i.ItemName?=?"Widget";
??????i.Description?=?"Regular?Widget";
??????i.Quantity?=?10;
??????i.UnitPrice?=?(decimal)?2.30;
??????i.Calculate();
??????//?Create?an?XmlTextWriter?using?a?FileStream.
??????Stream?fs?=?new?FileStream(filename,?FileMode.Create);
??????XmlWriter?writer?=?
??????new?XmlTextWriter(fs,?Encoding.Unicode);
??????//?Serialize?using?the?XmlTextWriter.
??????serializer.Serialize(writer,?i);
??????writer.Close();
???}
?private?void?DeserializeObject(string?filename)
???{???
??????Console.WriteLine("Reading?with?XmlReader");
??????//?Create?an?instance?of?the?XmlSerializer?specifying?type?and?namespace.
??????XmlSerializer?serializer?=?new?
??????XmlSerializer(typeof(OrderedItem));
??????//?A?FileStream?is?needed?to?read?the?XML?document.
??????FileStream?fs?=?new?FileStream(filename,?FileMode.Open);
??????XmlReader?reader?=?new?XmlTextReader(fs);
??????????
??????//?Declare?an?object?variable?of?the?type?to?be?deserialized.
??????OrderedItem?i;
??????//?Use?the?Deserialize?method?to?restore?the?object's?state.
??????i?=?(OrderedItem)?serializer.Deserialize(reader);
??????//?Write?out?the?properties?of?the?object.
??????Console.Write(
??????i.ItemName?+?"\t"?+
??????i.Description?+?"\t"?+
??????i.UnitPrice?+?"\t"?+
??????i.Quantity?+?"\t"?+
??????i.LineTotal);
???}
}
轉(zhuǎn)載于:https://www.cnblogs.com/waitrabbit/archive/2007/08/05/843578.html
總結(jié)
