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Groups > comp.lang.basic.visual.misc > #810

Re: What is a class?

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Farnsworth laid this down on his screen :
> "GS" <gs@somewhere.net> wrote in message news:jicag2$87f$1@dont-email.me...
>> Jim Mack wrote :
>>> What follows from that is that you can't then legitimately test "If x Is 
>>> Nothing" yourself, because doing so references X, and so creates it... 
>>> that's how you lose (some) control over object lifetime.
>>
>> I thought that the object created by "Dim As New" existed until the exit 
>> from the scope they were created in. So...
>>
>> In a procedure: (local scope)
>> Dim colItems As New Collection
>> ..lives for the entire procedure if not explicitly destroyed beforhand.
>>
>> In a module: (module scope)
>> Dim colItems As New Collection
>> ..lives for the duration code executes within the module if not explicitly 
>> destroyed beforhand.
>>
>> Global scope:
>> Dim colItems As New Collection
>> ..lives for the entire runtime if not explicitly destroyed beforhand.
>
> Correct, however, with "Dim As New", any checking to see if it's nothing 
> always creates the instance since you are referencing it. So "If o Is 
> Nothing" is always False in this case. Example:
>
> Option Explicit
>
> Private Sub Form_Load()
>     Dim o As New Collection
>
>     Debug.Print "o.Count = " & o.Count
>     Set o = Nothing
>
>     If o Is Nothing Then
>         Debug.Print "o Is Nothing"
>     Else
>         Debug.Print "o Is NOT Nothing"
>     End If
> End Sub
>
>
> Output:
>
> o.Count = 0
> o Is NOT Nothing
>
>
>
> Case 2: No New keyword at Dim:
>
> Option Explicit
>
> Private Sub Form_Load()
>     Dim o As Collection
>
>     Set o = New Collection
>
>     Debug.Print "o.Count = " & o.Count
>     Set o = Nothing
>
>     If o Is Nothing Then
>         Debug.Print "o Is Nothing"
>     Else
>         Debug.Print "o Is NOT Nothing"
>     End If
>
> End Sub
>
>
> Output:
>
> o.Count = 0
> o Is Nothing

As I replied to Ralph, I've heard this arg before but you and he are 
the first to demonstrate the facts behind the arg. I only use implicit 
instantiation in local scope as a rule because it just doesn't sit 
'right' with me to do this at module/global level.

Big thanks and appreciation for your persistence to get this across!

-- 
Garry

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What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-24 04:02 -0800
  Re: What is a class? "Auric__" <not.my.real@email.address> - 2012-02-24 14:06 +0000
    Re: What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-25 03:07 -0800
      Re: What is a class? Helmut_Meukel <Helmut_Meukel@bn-hof.invalid> - 2012-02-25 14:19 +0100
      Re: What is a class? "Auric__" <not.my.real@email.address> - 2012-02-25 21:26 +0000
        Re: What is a class? Jim Mack <no-uce-ube@mdxi.com> - 2012-02-25 18:58 -0500
          Re: What is a class? GS <gs@somewhere.net> - 2012-02-25 19:39 -0500
          Re: What is a class? "Auric__" <not.my.real@email.address> - 2012-02-26 03:09 +0000
            Re: What is a class? Jim Mack <no-uce-ube@mdxi.com> - 2012-02-25 22:35 -0500
              Re: What is a class? GS <gs@somewhere.net> - 2012-02-25 22:55 -0500
                Re: What is a class? "Farnsworth" <nospam@nospam.com> - 2012-02-25 23:27 -0500
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-26 01:30 -0500
                Re: What is a class? "Auric__" <not.my.real@email.address> - 2012-02-26 04:41 +0000
                Re: What is a class? ralph <nt_consulting64@yahoo.net> - 2012-02-25 23:05 -0600
                Re: What is a class? "Henning" <computer_hero@coldmail.com> - 2012-02-26 11:24 +0100
                Re: What is a class? ralph <nt_consulting64@yahoo.net> - 2012-02-25 23:03 -0600
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-26 01:26 -0500
                Re: What is a class? "Stuart McCall" <smccall@myunrealbox.com> - 2012-02-27 04:15 +0000
                Re: What is a class? ralph <nt_consulting64@yahoo.net> - 2012-02-27 00:48 -0600
                Re: What is a class? "Mayayana" <mayayana@invalid.nospam> - 2012-02-27 08:57 -0500
                Re: What is a class? "Stuart McCall" <smccall@myunrealbox.com> - 2012-02-27 19:19 +0000
                Re: What is a class? "Stuart McCall" <smccall@myunrealbox.com> - 2012-02-27 19:12 +0000
                Re: What is a class? "Bob Butler" <bob_butler@cox.invalid> - 2012-02-27 06:06 -0800
                Re: What is a class? "Stuart McCall" <smccall@myunrealbox.com> - 2012-02-27 19:24 +0000
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-27 11:01 -0500
                Re: What is a class? ralph <nt_consulting64@yahoo.net> - 2012-02-27 11:07 -0600
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-27 13:10 -0500
                Re: What is a class? Schmidt <sss@online.de> - 2012-02-27 19:09 +0100
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-27 13:29 -0500
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-27 14:43 -0500
                Re: What is a class? Schmidt <sss@online.de> - 2012-02-27 22:14 +0100
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-27 16:45 -0500
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-27 18:23 -0500
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-27 23:26 -0500
                Re: What is a class? Schmidt <sss@online.de> - 2012-02-28 13:54 +0100
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-28 08:37 -0500
                Re: What is a class? ralph <nt_consulting64@yahoo.net> - 2012-02-28 09:19 -0600
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-28 10:42 -0500
                Re: What is a class? Schmidt <sss@online.de> - 2012-02-29 06:47 +0100
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-29 09:39 -0500
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-29 13:33 -0500
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-29 14:43 -0500
                Re: What is a class? Schmidt <sss@online.de> - 2012-02-29 21:39 +0100
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-29 16:15 -0500
                Re: What is a class? Schmidt <sss@online.de> - 2012-02-29 23:20 +0100
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-28 00:16 -0500
                Re: What is a class? Jim Mack <no-uce-ube@mdxi.com> - 2012-02-27 13:26 -0500
                Re: What is a class? "Stuart McCall" <smccall@myunrealbox.com> - 2012-02-27 19:33 +0000
                Re: What is a class? Jim Mack <no-uce-ube@mdxi.com> - 2012-02-27 15:50 -0500
                Re: What is a class? Helmut_Meukel <Helmut_Meukel@bn-hof.invalid> - 2012-02-26 11:02 +0100
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-26 14:23 -0500
                Re: What is a class? GS <gs@somewhere.net> - 2012-02-26 17:09 -0500
            Re: What is a class? ralph <nt_consulting64@yahoo.net> - 2012-02-25 22:21 -0600
              Re: What is a class? "Auric__" <not.my.real@email.address> - 2012-02-26 04:51 +0000
                Re: What is a class? ralph <nt_consulting64@yahoo.net> - 2012-02-25 23:10 -0600
        Re: What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-26 04:11 -0800
          Re: What is a class? Helmut_Meukel <Helmut_Meukel@bn-hof.invalid> - 2012-02-26 16:37 +0100
          Re: What is a class? "Auric__" <not.my.real@email.address> - 2012-02-26 18:36 +0000
            Re: What is a class? ralph <nt_consulting64@yahoo.net> - 2012-02-26 14:11 -0600
            Re: What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-27 03:11 -0800
              Re: What is a class? "Auric__" <not.my.real@email.address> - 2012-02-27 16:33 +0000
                Re: What is a class? Jim Mack <no-uce-ube@mdxi.com> - 2012-02-27 13:33 -0500
                Re: What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-28 04:07 -0800
    Re: What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-25 03:33 -0800
    Re: What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-25 04:19 -0800
  Re: What is a class? "Ivar" <ivar.ekstromer000@ntlworld.com> - 2012-02-24 15:15 +0000
    Re: What is a class? GS <gs@somewhere.net> - 2012-02-24 14:52 -0500
      Re: What is a class? "Ivar" <ivar.ekstromer000@ntlworld.com> - 2012-02-24 23:10 +0000
        Re: What is a class? GS <gs@somewhere.net> - 2012-02-24 19:46 -0500
          Re: What is a class Way off Topic "Ivar" <ivar.ekstromer000@ntlworld.com> - 2012-02-25 02:20 +0000
            Re: What is a class Way off Topic GS <gs@somewhere.net> - 2012-02-25 16:57 -0500
        Re: What is a class? Helmut_Meukel <Helmut_Meukel@bn-hof.invalid> - 2012-02-25 11:36 +0100
    Re: What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-25 03:35 -0800
  Re: What is a class? Jim Mack <no-uce-ube@mdxi.com> - 2012-02-24 15:23 -0500
    Re: What is a class? "Auric__" <not.my.real@email.address> - 2012-02-25 01:33 +0000
    Re: What is a class? Peter Nolan <peter.nolan40@gmail.com> - 2012-02-25 03:09 -0800
  Re: What is a class? "Mayayana" <mayayana@invalid.nospam> - 2012-02-24 20:05 -0500

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