What are good design patterns for copying an object?

Question

I need to copy an object with a rather deep hierarchy of member variables (i.e. the object has several members of different types, each of which has several members of different types, etc.). A deep copy will require the implementation of the clone () method in many classes, which seems redundant for my application.

The solution I came up with is pretty simple, but I wonder, a bad idea. My solution is this:

• Determine the blank interface Settings.
• Define an interface with a name IsCopyablethat has methods getSettings()and applySettings(Settings s).
• For a given class Xthat implements IsCopyable, a class is written that implements an interface Settingsthat contains the “settings” that must be applied to the class object Xin order to copy it, (I usually insert this class into the class X, so I have one X.Settings implements Settings, but it can be done in another location.)

Then, to copy an instance of class X:

X myX = new X();
// Stuff happens to myX.
// Now we want to copy myX.
X copyOfX = new X();
copyOfX.applySettings(myX.getSettings());

Ie, to copy this object, create a new instance of this object, then call it getSettings()on the object you want to copy, passing the resulting object Settingsas a value applySettings()to the new instance. (Of course, copying can be wrapped in a member called copy () or something like that.)

, - ? () , ?

.

Answer 1

"" , :-) , , :

• ( ) , ( ). :

  • , ..., , .
  • , ? (, , , ).

• , . , - , ( ...), ( ). , , . , , , .

• , . , A, B. A C of B, A B ( C), B, , , . .

• , . ... , , , / Factory ( ), ( ):

  • A B , , , . HashMaps , , Map, .
  • , (Factory excepted). , , , ( ).
  • factory Spring -backed , Spring. (, , ...).

---

( ) . , , . , , . ...

: , , . :

• : B, C, A. , , , . , , , , .
• : ( ). , , , .
• ...

, . , , . :

• , CustomizedCopier, , . , .
• (JRE, ...), Map/Registry Map, , , . , , , .

---

, . , - (, ).

, , :

• toString() .
• equals() hashCode() .
• ( "reset" ).
• -
• Seriable ( HttpSession, ; , ).
• ...

, . , , . , ...

---

. , , , . , , , , ( , , ) .

Answer 2

, . " ", :

• value (struct #) . ( )
• , .
• " ", , . ( WCF )
• - , .

, , , factory, " " , ICloneable factory.

Answer 3

ICloneable inteface, http://blog.reamped.net/post/2008/03/Implementing-Interfaces-ICloneable-and-IComparable.aspx

Answer 4

, asp.net. , MemberwiseClone() - .

, , ICloneable, MemberwiseClone()

public class MyObject : ICloneable
{
   ...

   public object ICloneable.Clone()
   {
      MyObject clone = new MyObject();
      //copy everything I want to have from this object to the clone

      return clone;
   }
}

MyObject someObjInstance = new MyObject();
...
...
MyObject clone = ((ICloneable)someObjInstance).Clone();
...

, . , , , Clone(), , .

. , , MemberwiseClone().

Answer 5

Settings ( ), . , "I" ISettings.

applySettings(Settings s)? , , Settings , s, . "", , .

, applySettings(). , , . ( - ), . , : " ", " ".

Creating a deep copy should be simple from the point of view of the client. The interface is ICloneableperfect for this. As a design pattern, this is called the Prototype pattern . If you need different ways to create a copy (i.e., various deep copy operations), you can consider the Builder template to implement the methodClone()