[Dev-C++] Re: Singleton with Reference?

[Omar B. <oba...@gm...>]

Ok, sorry to reply myself but, after a bit of browsing aI have concluded
that my exact problem is in the lines 38 and 50 (see complete code below)

38 Singleton1 sing =3D Singleton1::getHandle();
50 Singleton1 sing2 =3D Singleton1::getHandle();

On these lines I was trying to get the handle to the actual object but
instead the compiler calls the default "copy constructor" (the compiler
makes is public by default):

Singleton1(Singleton1 const&){}

After I made this constructor private the complier throw me errors, so, if =
I
replace all the calls with a simple Singleton1.getHandle().getValues and
.printValues everything goes allright.

So my question now is, is there a way to achieve what I was trying to do in
lines 38 and 50, this is to save in a variable the "handler" to the actual
singleton variable ??

I know this is more a pure C++ issue [not a DevC++ specific issue) but and =
I
am sorry about that :)

Cheers,

Omar.

On 9/30/05, Omar Baqueiro <oba...@gm...> wrote:
>
> Hello, I am trying to make a singleton class using a reference to an
> object, this is the code:
>
> ---- BEGIN main.cpp ---
>
> 01 #include <cstdio>
> 02 #include <iostream>
> 03
> 04 /*
> 05 * Singleton class
> 06 */
> 07 class Singleton1
> 08 {
> 09 int a,b,c;
> 10
> 11 // class constructor
> 12 Singleton1(){}
> 13 public:
> 14 // class destructor
> 15 ~Singleton1(){}
> 16 static Singleton1 &getHandle()
> 17 {
> 18 static Singleton1 s; // create a static variable to preserve its value
> while the prgram is running
> 19 return s;
> 20 }
> 21 void setVars(int na, int nb, int nc)
> 22 {
> 23 a =3D na;
> 24 b =3D nb;
> 25 c =3D nc;
> 26 }
> 27 void printVars()
> 28 {
> 29 printf ("a: %d, b: %d, c: %d\n",a,b,c);
> 30 }
> 31
> 32 };
> 33
> 34 using namespace std;
> 35
> 36 int main(int argc, char *argv[])
> 37 {
> 38 Singleton1 sing =3D Singleton1::getHandle();
> 39
> 40 puts("vars a,b,c have trash:");
> 41 sing.printVars();
> 42
> 43 puts ("set vars to 1,2,3");
> 44 sing.setVars(1,2,3);
> 45
> 46 puts ("vars a,b,c should have 1,2,3, they have:");
> 47 sing.printVars();
> 48
> 49 puts ("Getting Singleton1 handler again...");
> 50 Singleton1 sing2 =3D Singleton1::getHandle();
> 51
> 52 puts("[using new handle] vars a,b,c should have 1,2,3, they have:");
> 53 sing2.printVars();
> 54
> 55 system("PAUSE");
> 56 return EXIT_SUCCESS;
> 57 }
>
> ---- EOF ---
>
> Now, the first lines until 49 on the main function behave as expected but=
,
> on line 50 I try to get again the handle to the singleton (via getHandle
> static function) but it returns another new variable so, the values (1,2 =
and
> 3 in this case) of the previous Singleton object are lost. Because of tha=
t
> line 53 will print 0,0,0 and not 1,2,3.
>
> Am I doing something wrong here?
>
> Now, I can make it work if I change the getHandle function to return a
> pointer ( Singleton1 * getHandle() ) and I change also the static variabl=
e
> [line 18] to
>
> 18 static Singleton1 s =3D new Singleton1();
>
> Of course I also change the references to the variable. But if I do it
> this way there is no way I can delete the dynamically allocated object. A=
nd
> I would like to do it using references and avoid pointers.
>
>
> Any clue?
>
> Cheers,
>
> Omar.
> --
> Omar Baqueiro Espinosa
> Computer Systems Engineer
> Home: www.csc.liv.ac.uk/~omar/ <http://www.csc.liv.ac.uk/%7Eomar/>
> Calendar: calendar.yahoo.com/obaqueiro
> <http://calendar.yahoo.com/obaqueiro>
> PGP Key available at: www.csc.liv.ac.uk/~omar/pgp.html<http://www.csc.liv=
.ac.uk/%7Eomar/pgp.html>
> _____
>



--
Omar Baqueiro Espinosa
Computer Systems Engineer
Home: www.csc.liv.ac.uk/~omar/ <http://www.csc.liv.ac.uk/~omar/>
Calendar: calendar.yahoo.com/obaqueiro <http://calendar.yahoo.com/obaqueiro=
>
PGP Key available at:
www.csc.liv.ac.uk/~omar/pgp.html<http://www.csc.liv.ac.uk/~omar/pgp.html>
_____