设计模式之：原型模式PrototypePattern的实现（浅克隆和深克隆）（浅表副本和深表副本）

Posted 2022-04-03 张德长

原型模式不是通过new生成新的对象，而使通过复制进行生成；

原型模式适用于相同类型的多个对象的生成；

原型模式分为两种：浅克隆/浅表副本（Shallow Clone）和深克隆/深表副本（Deep Clone）；

浅克隆：Shallow Clone，只复制值类型变量，不复制引用类型变量的克隆；（只复制引用类型变量的地址，其实还是指向同一个引用类型）

深克隆：Deep Clone，同时复制值类型和引用类型变量的克隆；

浅克隆用到的技术：

• Object.MemberwiseClone 方法（命名空间:System），使用该方法可以进行浅克隆；

深克隆用到的技术：

• BinaryFormatter 类（命名空间:System.Runtime.Serialization.Formatters.Binary），用来将需要克隆的类进行序列化和反序列化；
• FileStream 类 （命名空间:System.IO），用来将序列化的数据存储到临时文件中，克隆的时候从文件中读取数据；
• SerializationException 类（命名空间:System.Runtime.Serialization），用来捕获序列化/反序列化过程中的异常；
• SerializableAttribute 类（命名空间:System），用来对需要克隆的类进行标记，表示改类可以序列化；

类图 with StarUML

浅克隆Shallow Clone

internal class WeeklyLog
    
        private Attachment attachment;     
        public  Attachment Attachment  get => attachment; set => attachment = value;  
        /// <summary>
        /// 浅克隆
        /// </summary>
        /// <returns></returns>
        public WeeklyLog ShallowClone()
        
            return this.MemberwiseClone() as WeeklyLog;
        
    

    internal class Attachment
    
        private string name;
        public string Name  get => name; set => name = value; 
        public void DownLoad()  Console.WriteLine($"下载附件，文件名为：name"); 
    

    internal class Program
    
        static void Main(string[] args)
        
            WeeklyLog previousLog, newLog;
            previousLog = new WeeklyLog();

            Attachment attachment = new Attachment();
            previousLog.Attachment = attachment;
            newLog = previousLog.ShallowClone();

            Console.WriteLine("--浅表副本/浅克隆（Shallow Clone）的测试--");
            Console.WriteLine("周报是否相同？0", previousLog == newLog ? "是" : "否");
            Console.WriteLine("附件是否相同？0", (previousLog.Attachment == newLog.Attachment) ? "是" : "否");
            Console.Read();
        
    

运行结果

深克隆Deep Clone

[Serializable]
    internal class WeeklyLog
    
        private Attachment attachment;
        public Attachment Attachment  get => attachment; set => attachment = value; 
        /// <summary>
        /// 深克隆DeepClone
        /// </summary>
        /// <returns></returns>
        public WeeklyLog DeepClone()
        
            WeeklyLog clone = null;

            FileStream stream1 = new FileStream("Temp.dat", FileMode.Create);
            BinaryFormatter formatter1 = new BinaryFormatter();
            //序列化
            try  formatter1.Serialize(stream1, this); 
            catch (SerializationException ex)  Console.WriteLine($"序列化失败：ex.Message"); 
            finally  stream1.Close(); 

            FileStream stream2 = new FileStream("Temp.dat", FileMode.Open);
            BinaryFormatter formatter2 = new BinaryFormatter();
            //反序列化
            try  clone = formatter2.Deserialize(stream2) as WeeklyLog; 
            catch (SerializationException ex)  Console.WriteLine($"反序列化失败：ex.Message"); 
            finally  stream2.Close(); 

            return clone;
        
    

    [Serializable]
    internal class Attachment
    
        private string name;
        public string Name  get => name; set => name = value; 
        public void DownLoad()  Console.WriteLine($"下载附件，文件名为：name"); 
    

internal class Program
    
        static void Main(string[] args)
        
            WeeklyLog previousLog, newLog;
            previousLog = new WeeklyLog();

            Attachment attachment = new Attachment();
            previousLog.Attachment = attachment;
            newLog = previousLog.DeepClone();

            Console.WriteLine("--深表副本/深克隆（Deep Clone）的测试--");
            Console.WriteLine("周报是否相同？0", previousLog == newLog ? "是" : "否");
            Console.WriteLine("附件是否相同？0", (previousLog.Attachment == newLog.Attachment) ? "是" : "否");
            Console.Read();
        
    

 运行结果