Implement Prototype design mode
Implementing the prototype design pattern
When I build an instance of a class is very complicated, we can use the prototype mode. An instance of a large number of classes is established, it is better to use the original copy of the original instance after appropriate modification. Using the prototype mode, you can reduce the number of subclasses by cloning a prototype. Prototype mode can reduce the number of instances of classes.
In this mode, the object is created by cloning. We sometimes create a lot of subclasses, in addition to creating different objects through a lot of subclasses, we can only need a single subclass, this subclass keeps a reference to each object base class, and created through this subclass Object. Parameters and cloned the object by transmitting the parameters and cloned the object. Each object implements a Clone method, so it can be cloned. We can use the prototype mode to reduce the number of subclasses by cloning prototypes.
Clones can be implemented by implementing the IcloneAble interface. The only way in the iCloneable interface is Clone and returns an instance of a new class.
Icloneable.clone method Signature [VisualBasic] Function Clone () as object [c #] Object Clone ();
We must understand that the clone () method is just a shallow copying, not deep copy (Deep Copy). So it just returns a reference, not an instance of a replication as deep copy (Deep Copy). We can implement deep replication (Deep Copy) by using the iSerializable interface.
Another disadvantage is that each subclass of the prototype must implement Clone () method, sometimes, adding a Clone method is difficult.
In this example, I built the Empdata class and implemented the Icloneable interface and the iSerializable interface. The iCloneable interface needs to implement a Clone method so that the class can be copied. The iSerializable interface in order to achieve deep replication of EMPDATA classes (DEEP COPY). The method used is: Sequence of EMPDATA objects into a file, or the file is also sequenced into an EMPDATA object.
The EmpData class contains two methods: GetEmpData and Changeempdata. These two methods are used to get the EMPDATA object in a string (String), change the EMPDATA class. Each method can be called to verify the difference between Shallow Copy and Deep Copy. When the EMPDATA class changes, this change occurs simultaneously in the clone object of EmpData; in deep copy, this change does not appear when the EmpData object changes. Empdata's cloned object.
The constructor of the EMPDATA class reads the XML file and creates an EMP object.
XML file
VB.NET implementation
Imports system.xml
Imports system.io
Imports system.collections
Imports system.Runtime.Serialization
Imports system.runtime.serialization.formatters.binary
Implements Icloneable, iSerializablePrivate Arremp as ArrayList
Public Sub New ()
DIM Xmldoc as new xmldocument
Dim node as xmlnode
DIM Objemp as CEMP
Arremp = New ArrayList
XMLDoc.Load ("Empdata.xml")
For each node in xmldoc.documentelement.childNodes
Objemp = New CEMP
Objemp.fname = node.selectsinglenode ("firstname"). InnerText
Objemp.lname = node.selectsinglenode ("Lastname"). InnerText
Arremp.Add (Objem)
NEXT
End Sub
Public Sub New (Byval Info As SerializationInfo, ByVal Context As Street "
DIM INTINDEX AS INTEGER
DIM INTCOUNT AS INTEGER
DIM Objemp as CEMP
Arremp = New ArrayList
INTCOUNT = CINT (Info.getValue ("EMP_COUNT", GetType (String))))
For intindex = 0 to intcount - 1
Objemp = New CEMP (Info, Context, Intindex)
Arremp.Add (Objem)
NEXT
End Sub
Public Function Clone () As Object Implements IcloneAble.clone
Try
Return ME
Catch exception
MsgBox (ex.toswoting)
END TRY
END FUNCTION
Public Function Clone (Byval Deep As Boolean) AS Object
Try
IF Deep Then
Return createdeepcopy ()
Else
Return Clone ()
END IF
Catch exception
MsgBox (ex.toswoting)
END TRY
END FUNCTION
Private function creatededeepcopy () AS CEMPDATA
DIM ObjempCopy As Cempdata
Dim Objstream As Stream
Dim Objbinformatter as new binaryformatter
Try
Objstream = file.open ("EmpData.bin", filemode.create)
Objbinformatter.Serialize (Objstream, ME)
Objstream.close ()
Objstream = file.open ("Empdata.bin", FileMode.Open
Objempcopy = ctype (objbinformatter.deserialize (objstream), CEMPDATA)
Objstream.close ()
CreateDeepcopy = ObjempCopy
Catch exception
MsgBox (ex.toswoting)
END TRY
END FUNCTION
Public Sub GetObjectData (ByVal info As System.Runtime.Serialization.SerializationInfo, ByVal context As System.Runtime.Serialization.StreamingContext) Implements System.Runtime.Serialization.ISerializable.GetObjectDataDim intIndex As Integer
DIM Objemp as CEMP
Info.addValue ("EMP_COUNT", arremp.count)
For infindex = 0 to arremp.count - 1
Objemp = arremp (intIndex)
Objemp.GetObjectData (Info, Context, Intindex)
NEXT
End Sub
Public function getempdata () AS STRING
DIM INTCOUNT AS INTEGER
DIM STREMPDATA AS STRING
For intcount = 0 TO Arremp.count - 1
Strempdata = strempdata & ctype (arremp (intcount), CEMP) .fname & chr (9) & ctype (arremp (intcount), CEMP) .lname & chr (13)
NEXT
GetEmpdata = strempdata
END FUNCTION
Public Sub Changeempdata ()
DIM Objemp as CEMP
For Each Objemp in Arremp
Objemp.fname = "firstname"
Objemp.lname = "lastname"
NEXT
End Sub
END CLASS
Public Class CEMP
Private mstrfname as string
Private mstrlname as string
Public property fname () AS STRING
Get
FNAME = MSTRFNAME
END GET
Set (byval value as string)
mstrfname = value
End set
End Property
Public property lname () AS STRING
Get
LName = mstrlname
END GET
Set (byval value as string)
MStrlName = Value
End set
End Property
Public Sub New ()
End Sub
Public Sub New (Byval Info As SerializationInfo, Byval Context As StreamingContext, Byval Intentex AS Integer)
MStrFName = CSTR (INFO.GETVALUE ("Emp_FName" & infinDex, gettype (string))
MStrlName = CSTR (INFO.GETVALUE ("EMP_LNAME" & INTINDEX, GETTYPE (STRING)))
End Sub
Public Sub GetObjectData (byval Info As SerializationInfo, Byval Context As Street Info.addValue ("Emp_FName" & intIndex, mstrfname)
Info.addValue ("EMP_LNAME" & INTINDEX, MSTRLNAME)
End Sub
END CLASS
