can I call from one constructor another constructor ?

[Steven H]

Re: can I call from one constructor another constructor ?

On Wed, 30 Jun 2004 10:22:11 -0400, John Wood wrote:
[color=blue]
> I still don't get why they didn't add optional parameters in C#...
> Constructor overloads can get pretty messy, given all the permutations you
> have to provide.[/color]

coming from a language which didnt have the overload concept (vb old) iam
thankfull everyday that C# does.

all it done was force brain bending logic to get things going.

--
-------------------------------------------
Steven H, 3rd Year B.I.T. Otago Polytechnic

..net Geek

[Steven H]

Re: can I call from one constructor another constructor ?

On Wed, 30 Jun 2004 21:53:04 -0400, John Wood wrote:
[color=blue][color=green][color=darkred]
>>> "Daniel O'Connell [C# MVP]" <onyxkirx@--NOSPAM--comcast.net> wrote in
>>> message[/color][/color][/color]
[color=blue][color=green][color=darkred]
>>> I also think that methods like MyMethod(a,,,,, ,4,,,83,c) are pretty
>>> unreadable. <<[/color][/color]
>
> VBA actually has some nice optional parameter syntax, it allows you to
> specify the name of the parameter(s) in the method call, eg. MyMethod(
> category:=Citru sFruit, price:=1.45, weight:=6 );[/color]

iirc vb had it too, not that it matters im too lazy to type out all that.
[color=blue]
> C# could quite easily adopt this syntax, and allow it for non-optional
> paramaterized methods also.[/color]

god i hope not.


--
-------------------------------------------
Steven H, 3rd Year B.I.T. Otago Polytechnic

..net Geek

[Steven H]

Re: can I call from one constructor another constructor ?

On Wed, 30 Jun 2004 10:22:11 -0400, John Wood wrote:
[color=blue]
> I still don't get why they didn't add optional parameters in C#...
> Constructor overloads can get pretty messy, given all the permutations you
> have to provide.[/color]

coming from a language which didnt have the overload concept (vb old) iam
thankfull everyday that C# does.

all it done was force brain bending logic to get things going.

--
-------------------------------------------
Steven H, 3rd Year B.I.T. Otago Polytechnic

..net Geek

[Steven H]

Re: can I call from one constructor another constructor ?

On Wed, 30 Jun 2004 21:53:04 -0400, John Wood wrote:
[color=blue][color=green][color=darkred]
>>> "Daniel O'Connell [C# MVP]" <onyxkirx@--NOSPAM--comcast.net> wrote in
>>> message[/color][/color][/color]
[color=blue][color=green][color=darkred]
>>> I also think that methods like MyMethod(a,,,,, ,4,,,83,c) are pretty
>>> unreadable. <<[/color][/color]
>
> VBA actually has some nice optional parameter syntax, it allows you to
> specify the name of the parameter(s) in the method call, eg. MyMethod(
> category:=Citru sFruit, price:=1.45, weight:=6 );[/color]

iirc vb had it too, not that it matters im too lazy to type out all that.
[color=blue]
> C# could quite easily adopt this syntax, and allow it for non-optional
> paramaterized methods also.[/color]

god i hope not.


--
-------------------------------------------
Steven H, 3rd Year B.I.T. Otago Polytechnic

..net Geek

[Mark Round]

RE: can I call from one constructor another constructor ?

The short answer is no. The constructor constructs an instance of a class. A more correct 'if there is one' version of the example you have provided would be:

public class A
{
private int a = 0;
private int b = 0;
private int c = 0;

public A ()
{

// a, b, c are initialized by the default values. Calling another constructor
is not necessary.. }

public A (int a, int b, int c)
{
_a = a;
_b = b;
_c = c;
// Whatever code you want here.
}

public int A {
get {
return _a;
}
set {
_a = value;
}
}

// Accessors for B and C would be here
}

Hope this helps.

"Paul" wrote:
[color=blue]
> public class A
> {
> public A ()
> {
> // here I would like to call the second version of _ctor, how to
> accomplish this ?
> }
>
> public A (int a, int b, int c)
> {
> // some code
> }
> }
>
> Thanks for any advice,
> Paul
>
>
>[/color]

[Simon Smith]

Re: can I call from one constructor another constructor ?

A slightly longer answer is yes, by providing default values:

public class A {

public A(int a, int b, int c) {
...
}
public A() : this(1, 2, 3) {
...
}

}

--
Simon Smith
simon dot s at ghytred dot com
www.ghytred.com/NewsLook - NNTP Client for Outlook


On 06 Jul 2004 04:49, "Mark Round" wrote:[color=blue]
>The short answer is no. The constructor constructs an instance of a class.
>A more correct 'if there is one' version of the example you have provided
>would be:
>
>public class A
>{
>private int a = 0;
>private int b = 0;
>private int c = 0;
>
>public A ()
>{
>
>// a, b, c are initialized by the default values. Calling another constructor
>is not necessary.. }
>
>public A (int a, int b, int c)
>{
>_a = a;
>_b = b;
>_c = c;
>// Whatever code you want here.
>}
>
>public int A {
>get {
>return _a;
>}
>set {
>_a = value;
>}
>}
>
>// Accessors for B and C would be here
>}
>
>Hope this helps.
>
>"Paul" wrote:
>[color=green]
>> public class A
>> {
>> public A ()
>> {
>> // here I would like to call the second version of _ctor, how to
>> accomplish this ?
>> }
>>
>> public A (int a, int b, int c)
>> {
>> // some code
>> }
>> }
>>
>> Thanks for any advice,
>> Paul
>>
>>
>>[/color]
>
>
>
>
>[/color]


--
Simon Smith
simon dot s at ghytred dot com
www.ghytred.com/NewsLook - NNTP Client for Outlook

[Stano]

Re: can I call from one constructor another constructor ?

I know that this might be getting away from the original post, but I have a question about optional paramters in C#.

I originally developed a COM DLL using VB.NET which had an optional parameter in one of the methods. I ported the entire project to C# (as I decided C# was the way to go) but I was unable to work out how to redefine the COM interface in C# with an optional COM parameter.

In the end the COM interface was defined in VB.NET and the rest of the project was written using C#. I know that this isn't a big deal, but it's been bugging me for a while now. Does anyone have any ideas on how to do this?

Thanks.

"John Wood" wrote:
[color=blue]
> Incidentally, I typically use the essence pattern for constructing complex
> objects now.. saves having all those overloads cluttering the class.
>
> --
> John Wood
> EMail: first name, dot, last name, at priorganize.com
>
> "Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
> news:MPG.1b4cdb 754a08b4ef98ae1 1@msnews.micros oft.com...[color=green]
> > John Wood <j@ro.com> wrote:[color=darkred]
> > > > Yes you can - just as your code below, but using "this" instead of
> > > > "base".
> > > Yeah true you can (I admit I forgot), but I rarely use that because you[/color][/color]
> have[color=green][color=darkred]
> > > little control over when the referenced constructor is called (it always
> > > runs before the constructor body).[/color]
> >
> > That doesn't mean it's not useful though. I use it all the time when
> > providing constructs which effectively default various values - each
> > constructor calls a version with more parameters, either directly going
> > to the "full" one or going in stages. I believe this is fairly common.
> >
> > --
> > Jon Skeet - <skeet@pobox.co m>
> > http://www.pobox.com/~skeet
> > If replying to the group, please do not mail me too[/color]
>
>
>[/color]

[David Williams , VB.NET MVP]

Re: can I call from one constructor another constructor ?

As I start to dig into C#, this is one major issue that I have run into
also. According to the specs for C#, optional parameters are not
supported.



"Stano" <Stano@discussi ons.microsoft.c om> wrote in message
news:66BE422F-0C22-4DED-9EF2-0BB2287B6B24@mi crosoft.com:[color=blue]
> I know that this might be getting away from the original post, but I have
> a question about optional paramters in C#.
>
> I originally developed a COM DLL using VB.NET which had an optional
> parameter in one of the methods. I ported the entire project to C# (as I
> decided C# was the way to go) but I was unable to work out how to redefine
> the COM interface in C# with an optional COM parameter.
>
> In the end the COM interface was defined in VB.NET and the rest of the
> project was written using C#. I know that this isn't a big deal, but it's
> been bugging me for a while now. Does anyone have any ideas on how to do
> this?
>
> Thanks.
>
> "John Wood" wrote:
>[color=green]
> > Incidentally, I typically use the essence pattern for constructing
> > complex
> > objects now.. saves having all those overloads cluttering the class.
> >
> > --
> > John Wood
> > EMail: first name, dot, last name, at priorganize.com
> >
> > "Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
> > news:MPG.1b4cdb 754a08b4ef98ae1 1@msnews.micros oft.com...[color=darkred]
> > > John Wood <j@ro.com> wrote:
> > > > > Yes you can - just as your code below, but using "this" instead
> > > > > of
> > > > > "base".
> > > > Yeah true you can (I admit I forgot), but I rarely use that because
> > > > you[/color]
> > have[color=darkred]
> > > > little control over when the referenced constructor is called (it
> > > > always
> > > > runs before the constructor body).
> > >
> > > That doesn't mean it's not useful though. I use it all the time when
> > > providing constructs which effectively default various values - each
> > > constructor calls a version with more parameters, either directly
> > > going
> > > to the "full" one or going in stages. I believe this is fairly
> > > common.
> > >
> > > --
> > > Jon Skeet - <skeet@pobox.co m>
> > > http://www.pobox.com/~skeet
> > > If replying to the group, please do not mail me too[/color]
> >
> >
> >[/color][/color]

[Frank Wisniewski]

Re: can I call from one constructor another constructor ?

why not try not making them optional?

use overloaded constructors for all scenarios.

example vb:

public function DoSomething(x as string, y as string, z as optional string)
as string

converted to c#

public string DoSomething(str ing x, string y)
public string DoSomething(str ing x, string y, string z)

my vb syntax may not be completely correct but hopefully you get the point i
am trying to make

--
Frank Wisniewski MCSE 4.0, MCP+I, A+
f p w 2 3 @ h o t m a i l . c o m
<David Williams>; "VB.NET MVP" <davidd.NOSPAM. williams@earthl ink.net> wrote
in message news:OQhAivUaEH A.2816@TK2MSFTN GP11.phx.gbl...[color=blue]
> As I start to dig into C#, this is one major issue that I have run into
> also. According to the specs for C#, optional parameters are not
> supported.
>
>
>
> "Stano" <Stano@discussi ons.microsoft.c om> wrote in message
> news:66BE422F-0C22-4DED-9EF2-0BB2287B6B24@mi crosoft.com:[color=green]
> > I know that this might be getting away from the original post, but I[/color][/color]
have[color=blue][color=green]
> > a question about optional paramters in C#.
> >
> > I originally developed a COM DLL using VB.NET which had an optional
> > parameter in one of the methods. I ported the entire project to C# (as I
> > decided C# was the way to go) but I was unable to work out how to[/color][/color]
redefine[color=blue][color=green]
> > the COM interface in C# with an optional COM parameter.
> >
> > In the end the COM interface was defined in VB.NET and the rest of the
> > project was written using C#. I know that this isn't a big deal, but[/color][/color]
it's[color=blue][color=green]
> > been bugging me for a while now. Does anyone have any ideas on how to do
> > this?
> >
> > Thanks.
> >
> > "John Wood" wrote:
> >[color=darkred]
> > > Incidentally, I typically use the essence pattern for constructing
> > > complex
> > > objects now.. saves having all those overloads cluttering the class.
> > >
> > > --
> > > John Wood
> > > EMail: first name, dot, last name, at priorganize.com
> > >
> > > "Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
> > > news:MPG.1b4cdb 754a08b4ef98ae1 1@msnews.micros oft.com...
> > > > John Wood <j@ro.com> wrote:
> > > > > > Yes you can - just as your code below, but using "this" instead
> > > > > > of
> > > > > > "base".
> > > > > Yeah true you can (I admit I forgot), but I rarely use that[/color][/color][/color]
because[color=blue][color=green][color=darkred]
> > > > > you
> > > have
> > > > > little control over when the referenced constructor is called (it
> > > > > always
> > > > > runs before the constructor body).
> > > >
> > > > That doesn't mean it's not useful though. I use it all the time when
> > > > providing constructs which effectively default various values - each
> > > > constructor calls a version with more parameters, either directly
> > > > going
> > > > to the "full" one or going in stages. I believe this is fairly
> > > > common.
> > > >
> > > > --
> > > > Jon Skeet - <skeet@pobox.co m>
> > > > http://www.pobox.com/~skeet
> > > > If replying to the group, please do not mail me too
> > >
> > >
> > >[/color][/color]
>[/color]

[Stano]

Re: can I call from one constructor another constructor ?

It's a distant memory as this was some time ago, but I tried that, and as far as I am aware it didn't work as I was trying to keep the interface binary compatible with my previous definition in VB.NET, so that my clients could install the new version without having to change their code.

Anyway it's a distant memory now as all of my recent development has left the COM world behind, and should I develop any COM interfaces in the future I'll make sure that I keep away from Optional parameters. They're the devil's work ;)

Thanks.

"Frank Wisniewski" wrote:
[color=blue]
> why not try not making them optional?
>
> use overloaded constructors for all scenarios.
>
> example vb:
>
> public function DoSomething(x as string, y as string, z as optional string)
> as string
>
> converted to c#
>
> public string DoSomething(str ing x, string y)
> public string DoSomething(str ing x, string y, string z)
>
> my vb syntax may not be completely correct but hopefully you get the point i
> am trying to make
>
> --
> Frank Wisniewski MCSE 4.0, MCP+I, A+
> f p w 2 3 @ h o t m a i l . c o m
> <David Williams>; "VB.NET MVP" <davidd.NOSPAM. williams@earthl ink.net> wrote
> in message news:OQhAivUaEH A.2816@TK2MSFTN GP11.phx.gbl...[color=green]
> > As I start to dig into C#, this is one major issue that I have run into
> > also. According to the specs for C#, optional parameters are not
> > supported.
> >
> >
> >
> > "Stano" <Stano@discussi ons.microsoft.c om> wrote in message
> > news:66BE422F-0C22-4DED-9EF2-0BB2287B6B24@mi crosoft.com:[color=darkred]
> > > I know that this might be getting away from the original post, but I[/color][/color]
> have[color=green][color=darkred]
> > > a question about optional paramters in C#.
> > >
> > > I originally developed a COM DLL using VB.NET which had an optional
> > > parameter in one of the methods. I ported the entire project to C# (as I
> > > decided C# was the way to go) but I was unable to work out how to[/color][/color]
> redefine[color=green][color=darkred]
> > > the COM interface in C# with an optional COM parameter.
> > >
> > > In the end the COM interface was defined in VB.NET and the rest of the
> > > project was written using C#. I know that this isn't a big deal, but[/color][/color]
> it's[color=green][color=darkred]
> > > been bugging me for a while now. Does anyone have any ideas on how to do
> > > this?
> > >
> > > Thanks.
> > >
> > > "John Wood" wrote:
> > >
> > > > Incidentally, I typically use the essence pattern for constructing
> > > > complex
> > > > objects now.. saves having all those overloads cluttering the class.
> > > >
> > > > --
> > > > John Wood
> > > > EMail: first name, dot, last name, at priorganize.com
> > > >
> > > > "Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
> > > > news:MPG.1b4cdb 754a08b4ef98ae1 1@msnews.micros oft.com...
> > > > > John Wood <j@ro.com> wrote:
> > > > > > > Yes you can - just as your code below, but using "this" instead
> > > > > > > of
> > > > > > > "base".
> > > > > > Yeah true you can (I admit I forgot), but I rarely use that[/color][/color]
> because[color=green][color=darkred]
> > > > > > you
> > > > have
> > > > > > little control over when the referenced constructor is called (it
> > > > > > always
> > > > > > runs before the constructor body).
> > > > >
> > > > > That doesn't mean it's not useful though. I use it all the time when
> > > > > providing constructs which effectively default various values - each
> > > > > constructor calls a version with more parameters, either directly
> > > > > going
> > > > > to the "full" one or going in stages. I believe this is fairly
> > > > > common.
> > > > >
> > > > > --
> > > > > Jon Skeet - <skeet@pobox.co m>
> > > > > http://www.pobox.com/~skeet
> > > > > If replying to the group, please do not mail me too
> > > >
> > > >
> > > >[/color]
> >[/color]
>
>
>[/color]

[David Williams , VB.NET MVP]

Re: can I call from one constructor another constructor ?

Sure you can do this, however it would not be the same COM signature as
the VB.NET code. If the OP is trying to maintain COM interface
compatibility, then this is not viable.

HTH

David

"Frank Wisniewski" <fpw23@hotmail. com> wrote in message
news:40f4af6c$1 _1@Usenet.com:[color=blue]
> why not try not making them optional?
>
> use overloaded constructors for all scenarios.
>
> example vb:
>
> public function DoSomething(x as string, y as string, z as optional
> string)
> as string
>
> converted to c#
>
> public string DoSomething(str ing x, string y)
> public string DoSomething(str ing x, string y, string z)
>
> my vb syntax may not be completely correct but hopefully you get the point
> i
> am trying to make
>[/color]

[Frank Wisniewski]

Re: can I call from one constructor another constructor ?

Good Point, I didn't thing about breaking interfaces. I guess this is one
of those times where the small differences in the two languages will cause a
problem.
--
Frank Wisniewski MCSE 4.0, MCP+I, A+
f p w 2 3 @ h o t m a i l . c o m
"Stano" <Stano@discussi ons.microsoft.c om> wrote in message
news:D4CEC119-4483-47CB-AFFA-C43C7A6671D1@mi crosoft.com...[color=blue]
> It's a distant memory as this was some time ago, but I tried that, and as[/color]
far as I am aware it didn't work as I was trying to keep the interface
binary compatible with my previous definition in VB.NET, so that my clients
could install the new version without having to change their code.[color=blue]
>
> Anyway it's a distant memory now as all of my recent development has left[/color]
the COM world behind, and should I develop any COM interfaces in the future
I'll make sure that I keep away from Optional parameters. They're the
devil's work ;)[color=blue]
>
> Thanks.
>
> "Frank Wisniewski" wrote:
>[color=green]
> > why not try not making them optional?
> >
> > use overloaded constructors for all scenarios.
> >
> > example vb:
> >
> > public function DoSomething(x as string, y as string, z as optional[/color][/color]
string)[color=blue][color=green]
> > as string
> >
> > converted to c#
> >
> > public string DoSomething(str ing x, string y)
> > public string DoSomething(str ing x, string y, string z)
> >
> > my vb syntax may not be completely correct but hopefully you get the[/color][/color]
point i[color=blue][color=green]
> > am trying to make
> >
> > --
> > Frank Wisniewski MCSE 4.0, MCP+I, A+
> > f p w 2 3 @ h o t m a i l . c o m
> > <David Williams>; "VB.NET MVP" <davidd.NOSPAM. williams@earthl ink.net>[/color][/color]
wrote[color=blue][color=green]
> > in message news:OQhAivUaEH A.2816@TK2MSFTN GP11.phx.gbl...[color=darkred]
> > > As I start to dig into C#, this is one major issue that I have run[/color][/color][/color]
into[color=blue][color=green][color=darkred]
> > > also. According to the specs for C#, optional parameters are not
> > > supported.
> > >
> > >
> > >
> > > "Stano" <Stano@discussi ons.microsoft.c om> wrote in message
> > > news:66BE422F-0C22-4DED-9EF2-0BB2287B6B24@mi crosoft.com:
> > > > I know that this might be getting away from the original post, but I[/color]
> > have[color=darkred]
> > > > a question about optional paramters in C#.
> > > >
> > > > I originally developed a COM DLL using VB.NET which had an optional
> > > > parameter in one of the methods. I ported the entire project to C#[/color][/color][/color]
(as I[color=blue][color=green][color=darkred]
> > > > decided C# was the way to go) but I was unable to work out how to[/color]
> > redefine[color=darkred]
> > > > the COM interface in C# with an optional COM parameter.
> > > >
> > > > In the end the COM interface was defined in VB.NET and the rest of[/color][/color][/color]
the[color=blue][color=green][color=darkred]
> > > > project was written using C#. I know that this isn't a big deal, but[/color]
> > it's[color=darkred]
> > > > been bugging me for a while now. Does anyone have any ideas on how[/color][/color][/color]
to do[color=blue][color=green][color=darkred]
> > > > this?
> > > >
> > > > Thanks.
> > > >
> > > > "John Wood" wrote:
> > > >
> > > > > Incidentally, I typically use the essence pattern for constructing
> > > > > complex
> > > > > objects now.. saves having all those overloads cluttering the[/color][/color][/color]
class.[color=blue][color=green][color=darkred]
> > > > >
> > > > > --
> > > > > John Wood
> > > > > EMail: first name, dot, last name, at priorganize.com
> > > > >
> > > > > "Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
> > > > > news:MPG.1b4cdb 754a08b4ef98ae1 1@msnews.micros oft.com...
> > > > > > John Wood <j@ro.com> wrote:
> > > > > > > > Yes you can - just as your code below, but using "this"[/color][/color][/color]
instead[color=blue][color=green][color=darkred]
> > > > > > > > of
> > > > > > > > "base".
> > > > > > > Yeah true you can (I admit I forgot), but I rarely use that[/color]
> > because[color=darkred]
> > > > > > > you
> > > > > have
> > > > > > > little control over when the referenced constructor is called[/color][/color][/color]
(it[color=blue][color=green][color=darkred]
> > > > > > > always
> > > > > > > runs before the constructor body).
> > > > > >
> > > > > > That doesn't mean it's not useful though. I use it all the time[/color][/color][/color]
when[color=blue][color=green][color=darkred]
> > > > > > providing constructs which effectively default various values -[/color][/color][/color]
each[color=blue][color=green][color=darkred]
> > > > > > constructor calls a version with more parameters, either[/color][/color][/color]
directly[color=blue][color=green][color=darkred]
> > > > > > going
> > > > > > to the "full" one or going in stages. I believe this is fairly
> > > > > > common.
> > > > > >
> > > > > > --
> > > > > > Jon Skeet - <skeet@pobox.co m>
> > > > > > http://www.pobox.com/~skeet
> > > > > > If replying to the group, please do not mail me too
> > > > >
> > > > >
> > > > >
> > >[/color]
> >
> >
> >[/color][/color]