Constructor within a constructor

Question

Is this a bad idea? Does calling a generic private constructor within a public constructor create multiple instances, or is this a valid way of initializing class variables?

Private Class MyClass
    Dim _msg As String

    Sub New(ByVal name As String)
        Me.New()
        'Do stuff
    End Sub

    Sub New(ByVal name As String, ByVal age As Integer)
        Me.New()
        'Do stuff
    End Sub

    Private Sub New() 'Initializer constructor
        Me._msg = "Hello StackOverflow"
        'Initialize other variables
    End Sub
End Class

quickmeme.com/meme/3pwiuu

templatetypedef
– templatetypedef

2012-06-28 21:24:36 +00:00
Commented Jun 28, 2012 at 21:24 — templatetypedef
– templatetypedef, Commented Jun 28, 2012 at 21:24

Mark Byers · Accepted Answer · 2012-06-28 21:13:57Z

4

That's perfectly valid and a commonly used way to reuse constructor code. Only one object is instantiated.

answered Jun 28, 2012 at 21:13

Mark Byers

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Comments

John Koerner · Accepted Answer · 2012-06-28 21:18:34Z

2

It is a valid approach. There are some caveats with where the new function can be called:

The Sub New constructor can run only once when a class is created. It cannot be called explicitly anywhere other than in the first line of code of another constructor from either the same class or from a derived class.

Read more about the object lifetime on MSDN.

answered Jun 28, 2012 at 21:18

John Koerner

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1 Comment

Chiramisu Over a year ago

Most thorough answer and thanks for the link. Love reading documentation :) ... (not sarcasm :P)

Eric J. · Accepted Answer · 2012-06-28 21:14:15Z

1

Chaining constructors like this will certainly not create additional object instances.

It is desirable to only write code for a certain portion of initialization once. This is a common and valid initialization pattern.

answered Jun 28, 2012 at 21:14

Eric J.

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