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OlimilO

Intermediate

  • "OlimilO" is male
  • "OlimilO" started this thread

Posts: 277

Date of registration: Jan 18th 2009

Location: Germany

Occupation: software engineer

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Thursday, October 22nd 2009, 12:09pm

a few words on assigning objects

Hi,

in Jabaco all intrinsic primitive data types will be copied with the equal sign " = "
But if you want to assign one Object to another, the meaning could either be

a) to copy the reference or
b) to make a flat copy, also called a clone, of it.

solution to a: simply use the equal sign " = ".
solution to b: you could use the Cloneable-interface. but ... there is another possibility: create a copy constructor

example for all possibilities:

Jabaco Source

 
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Public Sub Command1_Click()
   
   'assigning simply the reference
   Dim a As New DummyBean("cafebabe")
   Dim b As DummyBean = a
   
   MsgBox a & " " & b
   b.Bean = "greenbeen"
   
   MsgBox a & " " & b
End Sub
Public Sub Command2_Click()
   'using the interface Cloneable.
   'It has no method at all, it's just a flag-interface.
   'You have to implement the Clone-method yourself
   Dim a As New DummyBean("cafebabe")
   Dim b As DummyBean = Cast(a.Clone, DummyBean)
   
   MsgBox a & " " & b
   
   b.Bean = "greenbean"
   
   MsgBox a & " " & b
End Sub
Public Sub Command3_Click()
   'using a copy constructor
   Dim a As New DummyBean("cafebabe")
   Dim b As New DummyBean(a)
   
   MsgBox a & " " & b
   
   b.Bean = "greenbean"
   
   MsgBox a & " " & b
End Sub

sample class for all possibliities:

Jabaco Source

 
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Option Explicit
Implements Cloneable
Private dummy As String
Public Sub DummyBean(bean As String)
   dummy = bean
End Sub
'copy constructor
Public Sub DummyBean(another As DummyBean)
   Me.dummy = another.dummy
End Sub
Public Property Get Bean() As String
   Bean = dummy
End Property
Public Property Let Bean(value As String)
   dummy = value
End Property
Public Function toString() As String
   toString = Bean
End Function
Public Function Clone() As Object
   'Clone uses the copy constructor
   'but it *must* return Object
   'so you need to cast in the last
   Clone = New DummyBean(Me)
End Function


regards
OlimilO

This post has been edited 1 times, last edit by "OlimilO" (Oct 22nd 2009, 12:15pm)

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